diff --git a/netwerk/test/unit/head_cache.js b/netwerk/test/unit/head_cache.js
index 7640c4e28f92..9bd1adb31744 100644
--- a/netwerk/test/unit/head_cache.js
+++ b/netwerk/test/unit/head_cache.js
@@ -1,3 +1,5 @@
+Components.utils.import('resource://gre/modules/XPCOMUtils.jsm');
+
 var _CSvc;
 function get_cache_service() {
   if (_CSvc)
diff --git a/netwerk/test/unit/test_304_responses.js b/netwerk/test/unit/test_304_responses.js
index aba2eff58b2e..6fafdbcdbf08 100644
--- a/netwerk/test/unit/test_304_responses.js
+++ b/netwerk/test/unit/test_304_responses.js
@@ -8,10 +8,18 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 var httpServer = null;
 const testFileName = "test_customConditionalRequest_304";
 const basePath = "/" + testFileName + "/";
-const baseURI = "http://localhost:4444" + basePath;
+
+XPCOMUtils.defineLazyGetter(this, "baseURI", function() {
+  return URL + basePath;
+});
+
 const unexpected304 = "unexpected304";
 const existingCached304 = "existingCached304";
 
@@ -46,7 +54,7 @@ function run_test() {
                                  alwaysReturn304Handler);
   httpServer.registerPathHandler(basePath + existingCached304,
                                  alwaysReturn304Handler);
-  httpServer.start(4444);
+  httpServer.start(-1);
   run_next_test();
 }
 
diff --git a/netwerk/test/unit/test_307_redirect.js b/netwerk/test/unit/test_307_redirect.js
index da42c23492b0..28562ae312a2 100644
--- a/netwerk/test/unit/test_307_redirect.js
+++ b/netwerk/test/unit/test_307_redirect.js
@@ -5,9 +5,19 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
+XPCOMUtils.defineLazyGetter(this, "uri", function() {
+  return URL + "/redirect";
+});
+
+XPCOMUtils.defineLazyGetter(this, "noRedirectURI", function() {
+  return URL + "/content";
+});
+
 var httpserver = null;
-var uri = "http://localhost:4444/redirect";
-var noRedirectURI = "http://localhost:4444/content";
 
 function make_channel(url) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -69,7 +79,7 @@ function run_test()
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/redirect", redirectHandler);
   httpserver.registerPathHandler("/content", contentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var prefs = Cc["@mozilla.org/preferences-service;1"]
                 .getService(Components.interfaces.nsIPrefBranch);
diff --git a/netwerk/test/unit/test_NetUtil.js b/netwerk/test/unit/test_NetUtil.js
index e56cfa3c86b9..c3172a6afe64 100644
--- a/netwerk/test/unit/test_NetUtil.js
+++ b/netwerk/test/unit/test_NetUtil.js
@@ -200,11 +200,12 @@ function test_asyncFetch_with_nsIChannel()
     aResponse.setHeader("Content-Type", "text/plain", false);
     aResponse.write(TEST_DATA);
   });
-  server.start(4444);
+  server.start(-1);
 
   // Create our channel.
   let channel = NetUtil.ioService.
-                newChannel("http://localhost:4444/test", null, null);
+                newChannel("http://localhost:" +
+                           server.identity.primaryPort + "/test", null, null);
 
   // Open our channel asynchronously.
   NetUtil.asyncFetch(channel, function(aInputStream, aResult) {
@@ -234,10 +235,11 @@ function test_asyncFetch_with_nsIURI()
     aResponse.setHeader("Content-Type", "text/plain", false);
     aResponse.write(TEST_DATA);
   });
-  server.start(4444);
+  server.start(-1);
 
   // Create our URI.
-  let uri = NetUtil.newURI("http://localhost:4444/test");
+  let uri = NetUtil.newURI("http://localhost:" +
+                           server.identity.primaryPort + "/test");
 
   // Open our URI asynchronously.
   NetUtil.asyncFetch(uri, function(aInputStream, aResult) {
@@ -267,11 +269,12 @@ function test_asyncFetch_with_string()
     aResponse.setHeader("Content-Type", "text/plain", false);
     aResponse.write(TEST_DATA);
   });
-  server.start(4444);
+  server.start(-1);
 
   // Open our location asynchronously.
-  NetUtil.asyncFetch("http://localhost:4444/test", function(aInputStream,
-                                                            aResult) {
+  NetUtil.asyncFetch("http://localhost:" +
+                     server.identity.primaryPort + "/test",
+                     function(aInputStream, aResult) {
     // Check that we had success.
     do_check_true(Components.isSuccessCode(aResult));
 
diff --git a/netwerk/test/unit/test_XHR_redirects.js b/netwerk/test/unit/test_XHR_redirects.js
index ad98c88da0c5..8f1abc7b6ff6 100644
--- a/netwerk/test/unit/test_XHR_redirects.js
+++ b/netwerk/test/unit/test_XHR_redirects.js
@@ -17,8 +17,12 @@ var sOther;
 const BUGID = "676059";
 const OTHERBUGID = "696849";
 
-const pSame = 4444;
-const pOther = 4445;
+XPCOMUtils.defineLazyGetter(this, "pSame", function() {
+  return sSame.identity.primaryPort;
+});
+XPCOMUtils.defineLazyGetter(this, "pOther", function() {
+  return sOther.identity.primaryPort;
+});
 
 function createXHR(async, method, path)
 {
@@ -63,12 +67,12 @@ function run_test() {
 
   // same-origin target
   sSame.registerPathHandler("/bug" + BUGID + "-target", echoMethod);
-  sSame.start(pSame);
+  sSame.start(-1);
 
   // cross-origin target
   sOther = new HttpServer();
   sOther.registerPathHandler("/bug" + OTHERBUGID + "-target", echoMethod);
-  sOther.start(pOther);
+  sOther.start(-1);
 
   // format: redirectType, methodToSend, redirectedMethod, finalStatus
   //   redirectType sets the URI the initial request goes to
diff --git a/netwerk/test/unit/test_assoc.js b/netwerk/test/unit/test_assoc.js
index f4ddc8342e6b..059a01cdfb71 100644
--- a/netwerk/test/unit/test_assoc.js
+++ b/netwerk/test/unit/test_assoc.js
@@ -7,31 +7,42 @@ Cu.import("resource://testing-common/httpd.js");
 
 var httpserver = new HttpServer();
 var currentTestIndex = 0;
-var tests = [
-             // this is valid
-             {url: "/assoc/assoctest?valid",
-              responseheader: [ "Assoc-Req: GET http://localhost:4444/assoc/assoctest?valid",
-                                "Pragma: X-Verify-Assoc-Req" ],
-              flags : 0},
 
-             // this is invalid because the method is wrong
-             {url: "/assoc/assoctest?invalid",
-              responseheader: [ "Assoc-Req: POST http://localhost:4444/assoc/assoctest?invalid",
-                                "Pragma: X-Verify-Assoc-Req" ],
-              flags : CL_EXPECT_LATE_FAILURE},
-             
-             // this is invalid because the url is wrong
-             {url: "/assoc/assoctest?notvalid",
-              responseheader: [ "Assoc-Req: GET http://localhost:4444/wrongpath/assoc/assoctest?notvalid",
-                                "Pragma: X-Verify-Assoc-Req" ],
-              flags : CL_EXPECT_LATE_FAILURE},
+XPCOMUtils.defineLazyGetter(this, "port", function() {
+    return httpserver.identity.primaryPort;
+});
+
+XPCOMUtils.defineLazyGetter(this, "tests", function() {
+    return [
+            // this is valid
+            {url: "/assoc/assoctest?valid",
+             responseheader: ["Assoc-Req: GET http://localhost:" + port +
+                              "/assoc/assoctest?valid",
+                              "Pragma: X-Verify-Assoc-Req"],
+             flags: 0},
+
+            // this is invalid because the method is wrong
+            {url: "/assoc/assoctest?invalid",
+             responseheader: ["Assoc-Req: POST http://localhost:" + port +
+                              "/assoc/assoctest?invalid",
+                              "Pragma: X-Verify-Assoc-Req"],
+             flags: CL_EXPECT_LATE_FAILURE},
+
+            // this is invalid because the url is wrong
+            {url: "/assoc/assoctest?notvalid",
+             responseheader: ["Assoc-Req: GET http://localhost:" + port +
+                              "/wrongpath/assoc/assoctest?notvalid",
+                              "Pragma: X-Verify-Assoc-Req"],
+             flags: CL_EXPECT_LATE_FAILURE},
 
              // this is invalid because the space between method and URL is missing
-             {url: "/assoc/assoctest?invalid2",
-              responseheader: [ "Assoc-Req: GEThttp://localhost:4444/assoc/assoctest?invalid2",
-                                "Pragma: X-Verify-Assoc-Req" ],
-              flags : CL_EXPECT_LATE_FAILURE},
-];
+            {url: "/assoc/assoctest?invalid2",
+             responseheader: ["Assoc-Req: GEThttp://localhost:" + port +
+                              "/assoc/assoctest?invalid2",
+                              "Pragma: X-Verify-Assoc-Req"],
+             flags: CL_EXPECT_LATE_FAILURE},
+    ];
+});
 
 var oldPrefVal;
 var domBranch;
@@ -40,7 +51,7 @@ function setupChannel(url)
 {
     var ios = Components.classes["@mozilla.org/network/io-service;1"].
                          getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + url, "", null);
+    var chan = ios.newChannel("http://localhost:" + port + url, "", null);
     return chan;
 }
 
@@ -71,7 +82,7 @@ function run_test()
     domBranch.setBoolPref("enforce", true);
 
     httpserver.registerPathHandler("/assoc/assoctest", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     startIter();
     do_test_pending();
diff --git a/netwerk/test/unit/test_auth_proxy.js b/netwerk/test/unit/test_auth_proxy.js
index 888dc541638f..34d40e80f838 100644
--- a/netwerk/test/unit/test_auth_proxy.js
+++ b/netwerk/test/unit/test_auth_proxy.js
@@ -226,12 +226,12 @@ function run_test() {
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/", proxyAuthHandler);
   httpserv.identity.add("http", "somesite", 80);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   const prefs = Cc["@mozilla.org/preferences-service;1"]
                          .getService(Ci.nsIPrefBranch);
   prefs.setCharPref("network.proxy.http", "localhost");
-  prefs.setIntPref("network.proxy.http_port", 4444);
+  prefs.setIntPref("network.proxy.http_port", httpserv.identity.primaryPort);
   prefs.setCharPref("network.proxy.no_proxies_on", "");
   prefs.setIntPref("network.proxy.type", 1);
 
diff --git a/netwerk/test/unit/test_authentication.js b/netwerk/test/unit/test_authentication.js
index a7ad44908dc7..2e31395491f8 100644
--- a/netwerk/test/unit/test_authentication.js
+++ b/netwerk/test/unit/test_authentication.js
@@ -8,6 +8,14 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserv.identity.primaryPort;
+});
+
+XPCOMUtils.defineLazyGetter(this, "PORT", function() {
+  return httpserv.identity.primaryPort;
+});
+
 const FLAG_RETURN_FALSE   = 1 << 0;
 const FLAG_WRONG_PASSWORD = 1 << 1;
 const FLAG_BOGUS_USER = 1 << 2;
@@ -42,12 +50,12 @@ AuthPrompt1.prototype = {
     function ap1_promptUP(title, text, realm, savePW, user, pw)
   {
     // Note that the realm here isn't actually the realm. it's a pw mgr key.
-    do_check_eq("http://localhost:4444 (" + this.expectedRealm + ")", realm);
+    do_check_eq(URL + " (" + this.expectedRealm + ")", realm);
     if (text.indexOf(this.expectedRealm) == -1)
       do_throw("Text must indicate the realm");
     if (text.indexOf("localhost") == -1)
       do_throw("Text must indicate the hostname");
-    if (text.indexOf("4444") == -1)
+    if (text.indexOf(String(PORT)) == -1)
       do_throw("Text must indicate the port");
     if (text.indexOf("-1") != -1)
       do_throw("Text must contain negative numbers");
@@ -291,13 +299,13 @@ function run_test() {
   httpserv.registerPathHandler("/auth/realm", authRealm);
   httpserv.registerPathHandler("/auth/digest", authDigest);
 
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   tests[0]();
 }
 
 function test_noauth() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   listener.expectedCode = 401; // Unauthorized
   chan.asyncOpen(listener, null);
@@ -306,7 +314,7 @@ function test_noauth() {
 }
 
 function test_returnfalse1() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   chan.notificationCallbacks = new Requestor(FLAG_RETURN_FALSE, 1);
   listener.expectedCode = 401; // Unauthorized
@@ -316,7 +324,7 @@ function test_returnfalse1() {
 }
 
 function test_wrongpw1() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   chan.notificationCallbacks = new Requestor(FLAG_WRONG_PASSWORD, 1);
   listener.expectedCode = 200; // OK
@@ -326,7 +334,7 @@ function test_wrongpw1() {
 }
 
 function test_prompt1() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   chan.notificationCallbacks = new Requestor(0, 1);
   listener.expectedCode = 200; // OK
@@ -336,7 +344,7 @@ function test_prompt1() {
 }
 
 function test_returnfalse2() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   chan.notificationCallbacks = new Requestor(FLAG_RETURN_FALSE, 2);
   listener.expectedCode = 401; // Unauthorized
@@ -346,7 +354,7 @@ function test_returnfalse2() {
 }
 
 function test_wrongpw2() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   chan.notificationCallbacks = new Requestor(FLAG_WRONG_PASSWORD, 2);
   listener.expectedCode = 200; // OK
@@ -356,7 +364,7 @@ function test_wrongpw2() {
 }
 
 function test_prompt2() {
-  var chan = makeChan("http://localhost:4444/auth");
+  var chan = makeChan(URL + "/auth");
 
   chan.notificationCallbacks = new Requestor(0, 2);
   listener.expectedCode = 200; // OK
@@ -366,7 +374,7 @@ function test_prompt2() {
 }
 
 function test_ntlm() {
-  var chan = makeChan("http://localhost:4444/auth/ntlm/simple");
+  var chan = makeChan(URL + "/auth/ntlm/simple");
 
   chan.notificationCallbacks = new Requestor(FLAG_RETURN_FALSE, 2);
   listener.expectedCode = 401; // Unauthorized
@@ -376,7 +384,7 @@ function test_ntlm() {
 }
 
 function test_auth() {
-  var chan = makeChan("http://localhost:4444/auth/realm");
+  var chan = makeChan(URL + "/auth/realm");
 
   chan.notificationCallbacks = new RealmTestRequestor();
   listener.expectedCode = 401; // Unauthorized
@@ -386,7 +394,7 @@ function test_auth() {
 }
 
 function test_digest_noauth() {
-  var chan = makeChan("http://localhost:4444/auth/digest");
+  var chan = makeChan(URL + "/auth/digest");
 
   //chan.notificationCallbacks = new Requestor(FLAG_RETURN_FALSE, 2);
   listener.expectedCode = 401; // Unauthorized
@@ -396,7 +404,7 @@ function test_digest_noauth() {
 }
 
 function test_digest() {
-  var chan = makeChan("http://localhost:4444/auth/digest");
+  var chan = makeChan(URL + "/auth/digest");
 
   chan.notificationCallbacks = new Requestor(0, 2);
   listener.expectedCode = 200; // OK
@@ -406,7 +414,7 @@ function test_digest() {
 }
 
 function test_digest_bogus_user() {
-  var chan = makeChan("http://localhost:4444/auth/digest");
+  var chan = makeChan(URL + "/auth/digest");
   chan.notificationCallbacks =  new Requestor(FLAG_BOGUS_USER, 2);
   listener.expectedCode = 401; // unauthorized
   chan.asyncOpen(listener, null);
diff --git a/netwerk/test/unit/test_bug203271.js b/netwerk/test/unit/test_bug203271.js
index dae8c14f7531..3ba426cefb5d 100644
--- a/netwerk/test/unit/test_bug203271.js
+++ b/netwerk/test/unit/test_bug203271.js
@@ -101,7 +101,9 @@ function logit(i, data, ctx) {
 function setupChannel(suffix, value) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"].
                          getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+                              httpserver.identity.primaryPort + suffix,
+                              "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.requestMethod = "GET"; // default value, just being paranoid...
     httpChan.setRequestHeader("x-request", value, false);
@@ -131,7 +133,7 @@ function checkValueAndTrigger(request, data, ctx) {
 
 function run_test() {
     httpserver.registerPathHandler("/precedence", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // clear cache
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug248970_cookie.js b/netwerk/test/unit/test_bug248970_cookie.js
index db335ffd0a61..dba7e00072d2 100644
--- a/netwerk/test/unit/test_bug248970_cookie.js
+++ b/netwerk/test/unit/test_bug248970_cookie.js
@@ -18,7 +18,7 @@ function inChildProcess() {
 }
 function makeChan(path) {
   var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444/" + path, null, null)
+  var chan = ios.newChannel("http://localhost:" + httpserver.identity.primaryPort + "/" + path, null, null)
                 .QueryInterface(Ci.nsIHttpChannel);
   return chan;
 }
@@ -73,7 +73,7 @@ function run_test() {
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/set", setHandler);
   httpserver.registerPathHandler("/present", presentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
   
   do_test_pending();
   
diff --git a/netwerk/test/unit/test_bug263127.js b/netwerk/test/unit/test_bug263127.js
index 5fdf6b3dc541..41dbec5fef76 100644
--- a/netwerk/test/unit/test_bug263127.js
+++ b/netwerk/test/unit/test_bug263127.js
@@ -40,12 +40,13 @@ var listener = {
 function run_test() {
   // start server
   server = new HttpServer();
-  server.start(4444);
+  server.start(-1);
 
   // Initialize downloader
   var channel = Cc["@mozilla.org/network/io-service;1"]
                   .getService(Ci.nsIIOService)
-                  .newChannel("http://localhost:4444/", null, null);
+                  .newChannel("http://localhost:" +
+                              server.identity.primaryPort + "/", null, null);
 
   var targetFile = Cc["@mozilla.org/file/directory_service;1"]
                      .getService(Ci.nsIProperties)
diff --git a/netwerk/test/unit/test_bug331825.js b/netwerk/test/unit/test_bug331825.js
index 2031f6de043e..d34995eb95af 100644
--- a/netwerk/test/unit/test_bug331825.js
+++ b/netwerk/test/unit/test_bug331825.js
@@ -25,13 +25,14 @@ function run_test() {
 
   server.registerPathHandler("/bug" + BUGID, bug331825);
 
-  server.start(4444);
+  server.start(-1);
 
   // make request
   var channel =
       Components.classes["@mozilla.org/network/io-service;1"].
       getService(Components.interfaces.nsIIOService).
-      newChannel("http://localhost:4444/bug" + BUGID, null, null);
+      newChannel("http://localhost:" + server.identity.primaryPort + "/bug" +
+                 BUGID, null, null);
 
   channel.QueryInterface(Components.interfaces.nsIHttpChannel);
   channel.setRequestHeader("If-None-Match", "foobar", false);
diff --git a/netwerk/test/unit/test_bug369787.js b/netwerk/test/unit/test_bug369787.js
index 829629bd1e99..a35f7c83eb56 100644
--- a/netwerk/test/unit/test_bug369787.js
+++ b/netwerk/test/unit/test_bug369787.js
@@ -56,13 +56,14 @@ function run_test() {
 
   server.registerPathHandler("/bug" + BUGID, bug369787);
 
-  server.start(4444);
+  server.start(-1);
 
   // make request
   channel =
       Components.classes["@mozilla.org/network/io-service;1"].
       getService(Components.interfaces.nsIIOService).
-      newChannel("http://localhost:4444/bug" + BUGID, null, null);
+      newChannel("http://localhost:" +
+                 server.identity.primaryPort + "/bug" + BUGID, null, null);
 
   channel.QueryInterface(Components.interfaces.nsIHttpChannel);
   channel.asyncOpen(new TestListener(), null);
diff --git a/netwerk/test/unit/test_bug412945.js b/netwerk/test/unit/test_bug412945.js
index 48d9450dcb67..bb0adb44308b 100644
--- a/netwerk/test/unit/test_bug412945.js
+++ b/netwerk/test/unit/test_bug412945.js
@@ -22,13 +22,14 @@ function run_test() {
 
   httpserv.registerPathHandler("/bug412945", bug412945);
 
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   // make request
   var channel =
       Components.classes["@mozilla.org/network/io-service;1"].
       getService(Components.interfaces.nsIIOService).
-      newChannel("http://localhost:4444/bug412945", null, null);
+      newChannel("http://localhost:" + httpserv.identity.primaryPort +
+                 "/bug412945", null, null);
 
   channel.QueryInterface(Components.interfaces.nsIHttpChannel);
   channel.requestMethod = "post";
diff --git a/netwerk/test/unit/test_bug468426.js b/netwerk/test/unit/test_bug468426.js
index 7481fc04b1f1..d50cdb4c99f1 100644
--- a/netwerk/test/unit/test_bug468426.js
+++ b/netwerk/test/unit/test_bug468426.js
@@ -40,7 +40,8 @@ var tests = [
 function setupChannel(suffix, value, cookie) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"]
             .getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+                             httpserver.identity.primaryPort + suffix, "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.requestMethod = "GET";
     httpChan.setRequestHeader("x-request", value, false);
@@ -69,7 +70,7 @@ function checkValueAndTrigger(request, data, ctx) {
 
 function run_test() {
     httpserver.registerPathHandler("/bug468426", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // Clear cache and trigger the first test
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug468594.js b/netwerk/test/unit/test_bug468594.js
index 94f4c03e1582..6b908a2d6ecb 100644
--- a/netwerk/test/unit/test_bug468594.js
+++ b/netwerk/test/unit/test_bug468594.js
@@ -62,7 +62,7 @@ function logit(i, data) {
 function setupChannel(suffix, value) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"].
                          getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" + httpserver.identity.primaryPort + suffix, "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.requestMethod = "GET";
     httpChan.setRequestHeader("x-request", value, false);
@@ -88,7 +88,7 @@ function checkValueAndTrigger(request, data, ctx) {
 
 function run_test() {
     httpserver.registerPathHandler("/freshness", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // clear cache
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug482601.js b/netwerk/test/unit/test_bug482601.js
index 03d7825ff221..859f8702a346 100644
--- a/netwerk/test/unit/test_bug482601.js
+++ b/netwerk/test/unit/test_bug482601.js
@@ -50,7 +50,7 @@ function run_test() {
   httpserv.registerPathHandler("/bug482601/partial", bug482601_partial);
   httpserv.registerPathHandler("/bug482601/cached", bug482601_cached);
   httpserv.registerPathHandler("/bug482601/only_from_cache", bug482601_only_from_cache);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   var obs = Cc["@mozilla.org/observer-service;1"].getService();
   obs = obs.QueryInterface(Ci.nsIObserverService);
@@ -107,12 +107,14 @@ function storeCache(aCacheEntry, aResponseHeads, aContent) {
 function test_nocache() {
   observers_called = "";
 
-  var chan = makeChan("http://localhost:4444/bug482601/nocache");
+  var chan = makeChan("http://localhost:" + httpserv.identity.primaryPort +
+                      "/bug482601/nocache");
   chan.asyncOpen(listener, null);
 }
 
 function test_partial() {
-   asyncOpenCacheEntry("http://localhost:4444/bug482601/partial",
+   asyncOpenCacheEntry("http://localhost:" + httpserv.identity.primaryPort +
+                       "/bug482601/partial",
                        "HTTP",
                        Ci.nsICache.STORE_ANYWHERE,
                        Ci.nsICache.ACCESS_READ_WRITE,
@@ -133,12 +135,14 @@ function test_partial2(status, entry) {
 
   observers_called = "";
 
-  var chan = makeChan("http://localhost:4444/bug482601/partial");
+  var chan = makeChan("http://localhost:" + httpserv.identity.primaryPort +
+                      "/bug482601/partial");
   chan.asyncOpen(listener, null);
 }
 
 function test_cached() {
-   asyncOpenCacheEntry("http://localhost:4444/bug482601/cached",
+   asyncOpenCacheEntry("http://localhost:" + httpserv.identity.primaryPort +
+                       "/bug482601/cached",
                        "HTTP",
                        Ci.nsICache.STORE_ANYWHERE,
                        Ci.nsICache.ACCESS_READ_WRITE,
@@ -159,13 +163,15 @@ function test_cached2(status, entry) {
 
   observers_called = "";
 
-  var chan = makeChan("http://localhost:4444/bug482601/cached");
+  var chan = makeChan("http://localhost:" + httpserv.identity.primaryPort +
+                      "/bug482601/cached");
   chan.loadFlags = Ci.nsIRequest.VALIDATE_ALWAYS;
   chan.asyncOpen(listener, null);
 }
 
 function test_only_from_cache() {
-   asyncOpenCacheEntry("http://localhost:4444/bug482601/only_from_cache",
+   asyncOpenCacheEntry("http://localhost:" + httpserv.identity.primaryPort +
+                       "/bug482601/only_from_cache",
                        "HTTP",
                        Ci.nsICache.STORE_ANYWHERE,
                        Ci.nsICache.ACCESS_READ_WRITE,
@@ -186,7 +192,8 @@ function test_only_from_cache2(status, entry) {
 
   observers_called = "";
 
-  var chan = makeChan("http://localhost:4444/bug482601/only_from_cache");
+  var chan = makeChan("http://localhost:" + httpserv.identity.primaryPort +
+                      "/bug482601/only_from_cache");
   chan.loadFlags = Ci.nsICachingChannel.LOAD_ONLY_FROM_CACHE;
   chan.asyncOpen(listener, null);
 }
diff --git a/netwerk/test/unit/test_bug490095.js b/netwerk/test/unit/test_bug490095.js
index 671be29f67a6..a1713229c26b 100644
--- a/netwerk/test/unit/test_bug490095.js
+++ b/netwerk/test/unit/test_bug490095.js
@@ -49,7 +49,9 @@ function logit(i, data) {
 function setupChannel(suffix, value) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"].
                          getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+                              httpserver.identity.primaryPort +
+                              suffix, "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.requestMethod = "GET";
     httpChan.setRequestHeader("x-request", value, false);
@@ -79,7 +81,7 @@ function checkValueAndTrigger(request, data, ctx) {
 
 function run_test() {
     httpserver.registerPathHandler("/freshness", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // clear cache
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug510359.js b/netwerk/test/unit/test_bug510359.js
index d1cb7b1d72e1..5c05ce0a8754 100644
--- a/netwerk/test/unit/test_bug510359.js
+++ b/netwerk/test/unit/test_bug510359.js
@@ -15,7 +15,9 @@ var tests = [
 function setupChannel(suffix, value) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"]
             .getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+                              httpserver.identity.primaryPort +
+                              suffix, "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.requestMethod = "GET";
     httpChan.setRequestHeader("x-request", value, false);
@@ -41,7 +43,7 @@ function checkValueAndTrigger(request, data, ctx) {
 
 function run_test() {
     httpserver.registerPathHandler("/bug510359", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // clear cache
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug528292.js b/netwerk/test/unit/test_bug528292.js
index 62addc29c985..267895f21908 100644
--- a/netwerk/test/unit/test_bug528292.js
+++ b/netwerk/test/unit/test_bug528292.js
@@ -7,11 +7,23 @@ Cu.import("resource://testing-common/httpd.js");
 
 const sentCookieVal     = "foo=bar";
 const responseBody      = "response body";
-const baseURL           = "http://localhost:4444";
+
+XPCOMUtils.defineLazyGetter(this, "baseURL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 const preRedirectPath   = "/528292/pre-redirect";
-const preRedirectURL    = baseURL + preRedirectPath;
+
+XPCOMUtils.defineLazyGetter(this, "preRedirectURL", function() {
+  return baseURL + preRedirectPath;
+});
+
 const postRedirectPath  = "/528292/post-redirect";
-const postRedirectURL   = baseURL + postRedirectPath;
+
+XPCOMUtils.defineLazyGetter(this, "postRedirectURL", function() {
+  return baseURL + postRedirectPath;
+});
+
 var   httpServer        = null;
 var   receivedCookieVal = null;
 
@@ -35,7 +47,7 @@ function run_test()
   httpServer = new HttpServer();
   httpServer.registerPathHandler(preRedirectPath, preRedirectHandler);
   httpServer.registerPathHandler(postRedirectPath, postRedirectHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   // Disable third-party cookies in general.
   Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch).
diff --git a/netwerk/test/unit/test_bug536324_64bit_content_length.js b/netwerk/test/unit/test_bug536324_64bit_content_length.js
index 4148205ccd49..3423137fad66 100644
--- a/netwerk/test/unit/test_bug536324_64bit_content_length.js
+++ b/netwerk/test/unit/test_bug536324_64bit_content_length.js
@@ -51,7 +51,8 @@ function hugeContentLength(metadata, response) {
 
 function test_hugeContentLength() {
   var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444/", null, null)
+  var chan = ios.newChannel("http://localhost:" +
+                            httpServer.identity.primaryPort + "/", null, null)
                 .QueryInterface(Ci.nsIHttpChannel);
   chan.asyncOpen(listener, null);
 }
@@ -61,6 +62,6 @@ add_test(test_hugeContentLength);
 function run_test() {
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/", hugeContentLength);
-  httpServer.start(4444);
+  httpServer.start(-1);
   run_next_test();
 }
diff --git a/netwerk/test/unit/test_bug561276.js b/netwerk/test/unit/test_bug561276.js
index 03826e6cade3..0202de5ba36d 100644
--- a/netwerk/test/unit/test_bug561276.js
+++ b/netwerk/test/unit/test_bug561276.js
@@ -18,7 +18,8 @@ function setupChannel(suffix)
     var ios =
         Components.classes["@mozilla.org/network/io-service;1"]
         .getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+			     httpserver.identity.primaryPort + suffix, "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.requestMethod = "GET";
     return httpChan;
@@ -34,7 +35,7 @@ function run_test()
 {
     httpserver.registerPathHandler("/redirect1", redirectHandler1);
     httpserver.registerPathHandler("/redirect2", redirectHandler2);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // clear cache
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug586908.js b/netwerk/test/unit/test_bug586908.js
index d726a641c5db..b545732a0aa4 100644
--- a/netwerk/test/unit/test_bug586908.js
+++ b/netwerk/test/unit/test_bug586908.js
@@ -10,29 +10,31 @@ var httpserv = null;
 const CID = Components.ID("{5645d2c1-d6d8-4091-b117-fe7ee4027db7}");
 const contractID = "@mozilla.org/system-proxy-settings;1"
 
-var systemSettings = {
-  QueryInterface: function (iid) {
-    if (iid.equals(Components.interfaces.nsISupports) ||
-        iid.equals(Components.interfaces.nsIFactory) ||
-        iid.equals(Components.interfaces.nsISystemProxySettings))
-      return this;
-    throw Components.results.NS_ERROR_NO_INTERFACE;
-  },
-  createInstance: function (outer, iid) {
-    if (outer)
-      throw Components.results.NS_ERROR_NO_AGGREGATION;
-    return this.QueryInterface(iid);
-  },
-  lockFactory: function (lock) {
-    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
-  },
-  
-  mainThreadOnly: true,
-  PACURI: "http://localhost:4444/redirect",
-  getProxyForURI: function(aURI) {
-    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
-  }
-};
+XPCOMUtils.defineLazyGetter(this, "systemSettings", function() {
+  return {
+    QueryInterface: function (iid) {
+      if (iid.equals(Components.interfaces.nsISupports) ||
+          iid.equals(Components.interfaces.nsIFactory) ||
+          iid.equals(Components.interfaces.nsISystemProxySettings))
+        return this;
+      throw Components.results.NS_ERROR_NO_INTERFACE;
+    },
+    createInstance: function (outer, iid) {
+      if (outer)
+        throw Components.results.NS_ERROR_NO_AGGREGATION;
+      return this.QueryInterface(iid);
+    },
+    lockFactory: function (lock) {
+      throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+    },
+
+    mainThreadOnly: true,
+    PACURI: "http://localhost:" + httpserv.identity.primaryPort + "/redirect",
+    getProxyForURI: function(aURI) {
+      throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+    }
+  };
+});
 
 function checkValue(request, data, ctx) {
   do_check_true(called);
@@ -54,7 +56,7 @@ function run_test() {
   httpserv.registerPathHandler("/redirect", redirect);
   httpserv.registerPathHandler("/pac", pac);
   httpserv.registerPathHandler("/target", target);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   Components.manager.nsIComponentRegistrar.registerFactory(
     CID,
@@ -71,7 +73,8 @@ function run_test() {
   // clear cache
   evict_cache_entries();
 
-  var chan = makeChan("http://localhost:4444/target");
+  var chan = makeChan("http://localhost:" + httpserv.identity.primaryPort +
+                      "/target");
   chan.asyncOpen(new ChannelListener(checkValue, null), null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_bug596443.js b/netwerk/test/unit/test_bug596443.js
index fdab8a5c96b5..8b51c31737b2 100644
--- a/netwerk/test/unit/test_bug596443.js
+++ b/netwerk/test/unit/test_bug596443.js
@@ -11,7 +11,9 @@ var expectedOnStopRequests = 3;
 function setupChannel(suffix, xRequest, flags) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"]
             .getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+                              httpserver.identity.primaryPort +
+                              suffix, "", null);
     if (flags)
         chan.loadFlags |= flags;
 
@@ -53,7 +55,7 @@ Listener.prototype = {
 
 function run_test() {
     httpserver.registerPathHandler("/bug596443", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // make sure we have a profile so we can use the disk-cache
     do_get_profile();
diff --git a/netwerk/test/unit/test_bug618835.js b/netwerk/test/unit/test_bug618835.js
index c681e57d26ac..b23083bf75be 100644
--- a/netwerk/test/unit/test_bug618835.js
+++ b/netwerk/test/unit/test_bug618835.js
@@ -34,7 +34,8 @@ InitialListener.prototype = {
     onStopRequest: function(request, context, status) {
         do_check_eq(1, numberOfCLHandlerCalls);
         do_execute_soon(function() {
-            var channel = setupChannel("http://localhost:4444/post");
+            var channel = setupChannel("http://localhost:" +
+                                       httpserv.identity.primaryPort + "/post");
             channel.requestMethod = "post";
             channel.asyncOpen(new RedirectingListener(), null);
         });
@@ -48,7 +49,8 @@ RedirectingListener.prototype = {
     onStopRequest: function(request, context, status) {
         do_check_eq(1, numberOfHandlerCalls);
         do_execute_soon(function() {
-            var channel = setupChannel("http://localhost:4444/post");
+            var channel = setupChannel("http://localhost:" +
+                                       httpserv.identity.primaryPort + "/post");
             channel.requestMethod = "post";
             channel.asyncOpen(new VerifyingListener(), null);
         });
@@ -62,7 +64,8 @@ VerifyingListener.prototype = {
     onStartRequest: function(request, context) { },
     onStopRequest: function(request, context, status) {
         do_check_eq(2, numberOfHandlerCalls);
-        var channel = setupChannel("http://localhost:4444/cl");
+        var channel = setupChannel("http://localhost:" +
+                                   httpserv.identity.primaryPort + "/cl");
         channel.asyncOpen(new FinalListener(), null);
     }
 };
@@ -83,13 +86,14 @@ function run_test() {
   httpserv.registerPathHandler("/cl", content_location);
   httpserv.registerPathHandler("/post", post_target);
   httpserv.registerPathHandler("/redirect", redirect_target);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   // Clear cache
   evict_cache_entries();
 
   // Load Content-Location URI into cache and start the chain of loads
-  var channel = setupChannel("http://localhost:4444/cl");
+  var channel = setupChannel("http://localhost:" +
+                             httpserv.identity.primaryPort + "/cl");
   channel.asyncOpen(new InitialListener(), null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_bug633743.js b/netwerk/test/unit/test_bug633743.js
index af7c61dbd498..6ef55d12b428 100644
--- a/netwerk/test/unit/test_bug633743.js
+++ b/netwerk/test/unit/test_bug633743.js
@@ -14,7 +14,9 @@ var httpserver = null;
 function make_channel(flags, vary, value) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
     getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444/bug633743", null, null);
+  var chan = ios.newChannel("http://localhost:" +
+                            httpserver.identity.primaryPort +
+                            "/bug633743", null, null);
   return chan.QueryInterface(Ci.nsIHttpChannel);
 }
 
@@ -182,7 +184,7 @@ function run_test() {
 
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/bug633743", handler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   run_next_test();
   do_test_pending();
diff --git a/netwerk/test/unit/test_bug650995.js b/netwerk/test/unit/test_bug650995.js
index 01e30d92e89b..3010541a1c0f 100644
--- a/netwerk/test/unit/test_bug650995.js
+++ b/netwerk/test/unit/test_bug650995.js
@@ -27,7 +27,9 @@ function repeatToLargerThan1K(data) {
 function setupChannel(suffix, value) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"]
             .getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+                              httpserver.identity.primaryPort +
+                              suffix, "", null);
     var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
     httpChan.setRequestHeader("x-request", value, false);
     
@@ -143,7 +145,7 @@ function TestCacheEntrySize(setSizeFunc, firstRequest, secondRequest, secondExpe
 function run_test()
 {
     httpserver.registerPathHandler("/bug650995", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     prefService.setBoolPref("browser.cache.offline.enable", false);
 
diff --git a/netwerk/test/unit/test_bug659569.js b/netwerk/test/unit/test_bug659569.js
index 45d7a8571b30..44671b241712 100644
--- a/netwerk/test/unit/test_bug659569.js
+++ b/netwerk/test/unit/test_bug659569.js
@@ -12,7 +12,9 @@ function setupChannel(suffix)
     var ios =
         Components.classes["@mozilla.org/network/io-service;1"]
         .getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + suffix, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+			      httpserver.identity.primaryPort +
+			      suffix, "", null);
     return chan;
 }
 
@@ -29,7 +31,7 @@ function run_test()
 
     httpserver.registerPathHandler("/redirect1", redirectHandler1);
     httpserver.registerPathHandler("/redirect2", redirectHandler2);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     // clear cache
     evict_cache_entries();
diff --git a/netwerk/test/unit/test_bug667907.js b/netwerk/test/unit/test_bug667907.js
index ef3b273dd0f0..d4fcfba1f504 100644
--- a/netwerk/test/unit/test_bug667907.js
+++ b/netwerk/test/unit/test_bug667907.js
@@ -9,8 +9,14 @@ var httpserver = null;
 var simplePath = "/simple";
 var normalPath = "/normal";
 var httpbody = "<html></html>";
-var uri1 = "http://localhost:4444" + simplePath;
-var uri2 = "http://localhost:4444" + normalPath;
+
+XPCOMUtils.defineLazyGetter(this, "uri1", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + simplePath;
+});
+
+XPCOMUtils.defineLazyGetter(this, "uri2", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + normalPath;
+});
 
 function make_channel(url) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -54,7 +60,7 @@ function run_test()
   httpserver = new HttpServer();
   httpserver.registerPathHandler(simplePath, simpleHandler);
   httpserver.registerPathHandler(normalPath, normalHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var channel = make_channel(uri1);
   channel.asyncOpen(new listener("text/plain", function() {
diff --git a/netwerk/test/unit/test_bug669001.js b/netwerk/test/unit/test_bug669001.js
index aa765b95323f..f8ba25c061c0 100644
--- a/netwerk/test/unit/test_bug669001.js
+++ b/netwerk/test/unit/test_bug669001.js
@@ -7,7 +7,10 @@ Cu.import("resource://testing-common/httpd.js");
 
 var httpServer = null;
 var path = "/bug699001";
-var URI = "http://localhost:4444" + path;
+
+XPCOMUtils.defineLazyGetter(this, "URI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + path;
+});
 
 function make_channel(url) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -93,7 +96,7 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler(path, handler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   do_test_pending();
 
diff --git a/netwerk/test/unit/test_bug770243.js b/netwerk/test/unit/test_bug770243.js
index ca71b0b87d52..26cdc46d130b 100644
--- a/netwerk/test/unit/test_bug770243.js
+++ b/netwerk/test/unit/test_bug770243.js
@@ -20,7 +20,8 @@ function addCreds(scheme, host)
 {
   var authMgr = Components.classes['@mozilla.org/network/http-auth-manager;1']
                           .getService(Ci.nsIHttpAuthManager);
-  authMgr.setAuthIdentity(scheme, host, 4444, "basic", "secret", "/", "", "user", "pass");
+  authMgr.setAuthIdentity(scheme, host, httpserv.identity.primaryPort,
+                          "basic", "secret", "/", "", "user", "pass");
 }
 
 function clearCreds()
@@ -33,7 +34,8 @@ function clearCreds()
 function makeChan() {
   var ios = Cc["@mozilla.org/network/io-service;1"]
                       .getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444/", null, null)
+  var chan = ios.newChannel("http://localhost:" +
+                            httpserv.identity.primaryPort + "/", null, null)
                 .QueryInterface(Ci.nsIHttpChannel);
   return chan;
 }
@@ -197,12 +199,12 @@ function run_test()
   
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/", handler);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   const prefs = Cc["@mozilla.org/preferences-service;1"]
                          .getService(Ci.nsIPrefBranch);
   prefs.setCharPref("network.proxy.http", "localhost");
-  prefs.setIntPref("network.proxy.http_port", 4444);
+  prefs.setIntPref("network.proxy.http_port", httpserv.identity.primaryPort);
   prefs.setCharPref("network.proxy.no_proxies_on", "");
   prefs.setIntPref("network.proxy.type", 1);
 
diff --git a/netwerk/test/unit/test_bug812167.js b/netwerk/test/unit/test_bug812167.js
index 3c34d054dec4..75d3fc64193c 100644
--- a/netwerk/test/unit/test_bug812167.js
+++ b/netwerk/test/unit/test_bug812167.js
@@ -15,9 +15,16 @@ Cu.import("resource://testing-common/httpd.js");
 var httpserver = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath1 = "/redirect-no-store/" + Math.random();
-var randomURI1 = "http://localhost:4444" + randomPath1;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI1", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + randomPath1;
+});
+
 var randomPath2 = "/redirect-expires-past/" + Math.random();
-var randomURI2 = "http://localhost:4444" + randomPath2;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI2", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + randomPath2;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -30,7 +37,8 @@ const responseBody = "response body";
 function redirectHandler_NoStore(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 302, "Found");
-  response.setHeader("Location", "http://localhost:4444/content", false);
+  response.setHeader("Location", "http://localhost:" +
+                     httpserver.identity.primaryPort + "/content", false);
   response.setHeader("Cache-control", "no-store");
   return;
 }
@@ -38,7 +46,8 @@ function redirectHandler_NoStore(metadata, response)
 function redirectHandler_ExpiresInPast(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 302, "Found");
-  response.setHeader("Location", "http://localhost:4444/content", false);
+  response.setHeader("Location", "http://localhost:" +
+                     httpserver.identity.primaryPort + "/content", false);
   response.setHeader("Expires", "-1");
   return;
 }
@@ -89,7 +98,7 @@ function run_test()
   httpserver.registerPathHandler(randomPath1, redirectHandler_NoStore);
   httpserver.registerPathHandler(randomPath2, redirectHandler_ExpiresInPast);
   httpserver.registerPathHandler("/content", contentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   run_test_no_store();
   do_test_pending();
diff --git a/netwerk/test/unit/test_cacheForOfflineUse_no-store.js b/netwerk/test/unit/test_cacheForOfflineUse_no-store.js
index fa0c1b267d85..71206e78ebbc 100644
--- a/netwerk/test/unit/test_cacheForOfflineUse_no-store.js
+++ b/netwerk/test/unit/test_cacheForOfflineUse_no-store.js
@@ -12,7 +12,11 @@ var httpServer = null;
 const testFileName = "test_nsHttpChannel_CacheForOfflineUse-no-store";
 const cacheClientID = testFileName + "|fake-group-id";
 const basePath = "/" + testFileName + "/";
-const baseURI = "http://localhost:4444" + basePath;
+
+XPCOMUtils.defineLazyGetter(this, "baseURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + basePath;
+});
+
 const normalEntry = "normal";
 const noStoreEntry = "no-store";
 
@@ -119,7 +123,7 @@ function run_test()
   httpServer = new HttpServer();
   httpServer.registerPathHandler(basePath + normalEntry, normalHandler);
   httpServer.registerPathHandler(basePath + noStoreEntry, noStoreHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
   run_next_test();
 }
 
diff --git a/netwerk/test/unit/test_cache_jar.js b/netwerk/test/unit/test_cache_jar.js
index fdd3d7df12c5..fe6d1f628aaf 100644
--- a/netwerk/test/unit/test_cache_jar.js
+++ b/netwerk/test/unit/test_cache_jar.js
@@ -7,6 +7,10 @@ Cu.import("resource://testing-common/httpd.js");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserv.identity.primaryPort + "/cached";
+});
+
 var httpserv = null;
 var handlers_called = 0;
 
@@ -42,7 +46,7 @@ var thirdTests = [[0, false, 0], [0, true, 0], [1, false, 1], [1, true, 1]];
 function run_all_tests() {
   for (let test of firstTests) {
     handlers_called = 0;
-    var chan = makeChan("http://localhost:4444/cached", test[0], test[1]);
+    var chan = makeChan(URL, test[0], test[1]);
     chan.asyncOpen(new ChannelListener(doneFirstLoad, test[2]), null);
     yield;
   }
@@ -62,7 +66,7 @@ function run_all_tests() {
 
   for (let test of secondTests) {
     handlers_called = 0;
-    var chan = makeChan("http://localhost:4444/cached", test[0], test[1]);
+    var chan = makeChan(URL, test[0], test[1]);
     chan.asyncOpen(new ChannelListener(doneFirstLoad, test[2]), null);
     yield;
   }
@@ -76,7 +80,7 @@ function run_all_tests() {
 
   for (let test of thirdTests) {
     handlers_called = 0;
-    var chan = makeChan("http://localhost:4444/cached", test[0], test[1]);
+    var chan = makeChan(URL, test[0], test[1]);
     chan.asyncOpen(new ChannelListener(doneFirstLoad, test[2]), null);
     yield;
   }
@@ -88,14 +92,14 @@ function run_test() {
   do_test_pending();
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/cached", cached_handler);
-  httpserv.start(4444);
+  httpserv.start(-1);
   gTests = run_all_tests();
   gTests.next();
 }
 
 function doneFirstLoad(req, buffer, expected) {
   // Load it again, make sure it hits the cache
-  var chan = makeChan("http://localhost:4444/cached", 0, false);
+  var chan = makeChan(URL, 0, false);
   chan.asyncOpen(new ChannelListener(doneSecondLoad, expected), null);
 }
 
diff --git a/netwerk/test/unit/test_cacheflags.js b/netwerk/test/unit/test_cacheflags.js
index 9dd36510ca73..d38df4e76ec0 100644
--- a/netwerk/test/unit/test_cacheflags.js
+++ b/netwerk/test/unit/test_cacheflags.js
@@ -5,11 +5,12 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
-var httpserver = null;
+var httpserver = new HttpServer();
+httpserver.start(-1);
 
 // Need to randomize, because apparently no one clears our cache
 var suffix = Math.random();
-var httpBase = "http://localhost:4444";
+var httpBase = "http://localhost:" + httpserver.identity.primaryPort;
 var httpsBase = "http://localhost:4445";
 var shortexpPath = "/shortexp" + suffix;
 var longexpPath = "/longexp/" + suffix;
@@ -312,13 +313,11 @@ function longexp2_handler(metadata, response) {
 }
 
 function run_test() {
-  httpserver = new HttpServer();
   httpserver.registerPathHandler(shortexpPath, shortexp_handler);
   httpserver.registerPathHandler(longexpPath, longexp_handler);
   httpserver.registerPathHandler(longexp2Path, longexp2_handler);
   httpserver.registerPathHandler(nocachePath, nocache_handler);
   httpserver.registerPathHandler(nostorePath, nostore_handler);
-  httpserver.start(4444);
 
   run_next_test();
   do_test_pending();
diff --git a/netwerk/test/unit/test_channel_close.js b/netwerk/test/unit/test_channel_close.js
index f78d191f4ace..13cde02b5684 100644
--- a/netwerk/test/unit/test_channel_close.js
+++ b/netwerk/test/unit/test_channel_close.js
@@ -5,6 +5,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var testpath = "/simple";
 var httpbody = "0123456789";
@@ -13,7 +17,7 @@ var live_channels = [];
 
 function run_test() {
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var local_channel;
 
@@ -39,7 +43,7 @@ function run_test() {
 
 function setupChannel(path) {
   var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + path, "", null);
+  var chan = ios.newChannel(URL + path, "", null);
   chan.QueryInterface(Ci.nsIHttpChannel);
   chan.requestMethod = "GET";
   return chan;
diff --git a/netwerk/test/unit/test_content_encoding_gzip.js b/netwerk/test/unit/test_content_encoding_gzip.js
index 2153b938d854..61b2686390f8 100644
--- a/netwerk/test/unit/test_content_encoding_gzip.js
+++ b/netwerk/test/unit/test_content_encoding_gzip.js
@@ -33,7 +33,8 @@ var tests = [
 function setupChannel(url) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"].
                          getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + url, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+			      httpserver.identity.primaryPort + url, "", null);
     return chan;
 }
 
@@ -54,7 +55,7 @@ function completeIter(request, data, ctx) {
 function run_test() {
     httpserver.registerPathHandler("/test/cegzip1", handler);
     httpserver.registerPathHandler("/test/cegzip2", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     startIter();
     do_test_pending();
diff --git a/netwerk/test/unit/test_content_sniffer.js b/netwerk/test/unit/test_content_sniffer.js
index a47f0c958c68..013134bab33f 100644
--- a/netwerk/test/unit/test_content_sniffer.js
+++ b/netwerk/test/unit/test_content_sniffer.js
@@ -84,21 +84,22 @@ function makeChan(url) {
   return chan;
 }
 
-var urls = [
+var httpserv = null;
+var urls = null;
+
+function run_test() {
+  httpserv = new HttpServer();
+  httpserv.start(-1);
+
+  urls = [
   // NOTE: First URL here runs without our content sniffer
   "data:" + unknownType + ", Some text",
   "data:" + unknownType + ", Text", // Make sure sniffing works even if we
                                     // used the unknown content sniffer too
   "data:text/plain, Some more text",
-  "http://localhost:4444"
+    "http://localhost:" + httpserv.identity.primaryPort
 ];
 
-var httpserv = null;
-
-function run_test() {
-  httpserv = new HttpServer();
-  httpserv.start(4444);
-
   Components.manager.nsIComponentRegistrar.registerFactory(snifferCID,
     "Unit test content sniffer", snifferContract, sniffer);
 
diff --git a/netwerk/test/unit/test_cookie_header.js b/netwerk/test/unit/test_cookie_header.js
index ff77fc914c0b..3644c3889fd0 100644
--- a/netwerk/test/unit/test_cookie_header.js
+++ b/netwerk/test/unit/test_cookie_header.js
@@ -8,6 +8,10 @@ const Cr = Components.results;
 Cu.import("resource://testing-common/httpd.js");
 Cu.import("resource://gre/modules/Services.jsm");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserv.identity.primaryPort + "/";
+});
+
 function inChildProcess() {
   return Cc["@mozilla.org/xre/app-info;1"]
            .getService(Ci.nsIXULRuntime)
@@ -59,7 +63,7 @@ var listener = {
 function makeChan() {
   var ios = Components.classes["@mozilla.org/network/io-service;1"]
                       .getService(Components.interfaces.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444/", null, null)
+  var chan = ios.newChannel(URL, null, null)
                 .QueryInterface(Components.interfaces.nsIHttpChannel);
 
   return chan;
@@ -73,7 +77,7 @@ function run_test() {
     Services.prefs.setIntPref("network.cookie.cookieBehavior", 0);
 
   httpserv = new HttpServer();
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   var chan = makeChan();
 
diff --git a/netwerk/test/unit/test_cookiejars.js b/netwerk/test/unit/test_cookiejars.js
index 97cb4a3fe6fb..972275675e06 100644
--- a/netwerk/test/unit/test_cookiejars.js
+++ b/netwerk/test/unit/test_cookiejars.js
@@ -13,6 +13,10 @@ const Ci = Components.interfaces;
 const Cu = Components.utils;
 const Cr = Components.results;
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 Cu.import("resource://testing-common/httpd.js");
 Cu.import("resource://gre/modules/Services.jsm");
 var httpserver = new HttpServer();
@@ -50,7 +54,7 @@ var i = 0;
 function setupChannel(path)
 {
   var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + path, "", null);
+  var chan = ios.newChannel(URL + path, "", null);
   chan.notificationCallbacks = tests[i].loadContext;
   chan.QueryInterface(Ci.nsIHttpChannel);
   return chan;
@@ -122,7 +126,7 @@ function run_test()
 
   httpserver.registerPathHandler(cookieSetPath, cookieSetHandler);
   httpserver.registerPathHandler(cookieCheckPath, cookieCheckHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   setCookie();
   do_test_pending();
diff --git a/netwerk/test/unit/test_duplicate_headers.js b/netwerk/test/unit/test_duplicate_headers.js
index d60e73fa47ab..8efbef49ce25 100644
--- a/netwerk/test/unit/test_duplicate_headers.js
+++ b/netwerk/test/unit/test_duplicate_headers.js
@@ -13,6 +13,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var index = 0;
 var test_flags = new Array();
@@ -20,7 +24,7 @@ var testPathBase = "/dupe_hdrs";
 
 function run_test()
 {
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   do_test_pending();
   run_test_number(1);
@@ -41,7 +45,7 @@ function setupChannel(url)
 {
   var ios = Components.classes["@mozilla.org/network/io-service;1"].
                        getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + url, "", null);
+  var chan = ios.newChannel(URL + url, "", null);
   var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
   return httpChan;
 }
@@ -197,7 +201,7 @@ function handler6(metadata, response)
   response.write("HTTP/1.0 301 Moved\r\n");
   response.write("Content-Type: text/plain\r\n");
   response.write("Content-Length: 30\r\n");
-  response.write("Location: http://localhost:4444/content\r\n");
+  response.write("Location: " + URL + "/content\r\n");
   response.write("Location: http://www.microsoft.com/\r\n");
   response.write("Connection: close\r\n");
   response.write("\r\n");
@@ -224,8 +228,8 @@ function handler7(metadata, response)
   response.write("Content-Type: text/plain\r\n");
   response.write("Content-Length: 30\r\n");
   // redirect to previous test handler that completes OK: test 5
-  response.write("Location: http://localhost:4444" + testPathBase + "5\r\n");
-  response.write("Location: http://localhost:4444" + testPathBase + "5\r\n");
+  response.write("Location: " + URL + testPathBase + "5\r\n");
+  response.write("Location: " + URL + testPathBase + "5\r\n");
   response.write("Connection: close\r\n");
   response.write("\r\n");
   response.write(body);
@@ -259,7 +263,7 @@ function handler8(metadata, response)
   response.write("Content-Type: text/plain\r\n");
   response.write("Content-Length: 30\r\n");
   // redirect to previous test handler that completes OK: test 4
-  response.write("Location: http://localhost:4444" + testPathBase + "4\r\n");
+  response.write("Location: " + URL + testPathBase + "4\r\n");
   response.write("Location:\r\n");
   response.write("Connection: close\r\n");
   response.write("\r\n");
@@ -287,10 +291,10 @@ function handler9(metadata, response)
   response.write("Content-Type: text/plain\r\n");
   response.write("Content-Length: 30\r\n");
   // redirect to previous test handler that completes OK: test 2 
-  response.write("Location: http://localhost:4444" + testPathBase + "2\r\n");
+  response.write("Location: " + URL + testPathBase + "2\r\n");
   response.write("Location:\r\n");
   // redirect to previous test handler that completes OK: test 4
-  response.write("Location: http://localhost:4444" + testPathBase + "4\r\n");
+  response.write("Location: " + URL + testPathBase + "4\r\n");
   response.write("Connection: close\r\n");
   response.write("\r\n");
   response.write(body);
@@ -588,7 +592,7 @@ function handler20(metadata, response)
   response.write("Content-Length: 30\r\n");
   // redirect to previous test handler that completes OK: test 4
   response.write("Location:\r\n");
-  response.write("Location: http://localhost:4444" + testPathBase + "4\r\n");
+  response.write("Location: " + URL + testPathBase + "4\r\n");
   response.write("Connection: close\r\n");
   response.write("\r\n");
   response.write(body);
diff --git a/netwerk/test/unit/test_event_sink.js b/netwerk/test/unit/test_event_sink.js
index d6aeb5e530ae..105c818633cb 100644
--- a/netwerk/test/unit/test_event_sink.js
+++ b/netwerk/test/unit/test_event_sink.js
@@ -7,6 +7,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserv.identity.primaryPort;
+});
+
 const sinkCID = Components.ID("{14aa4b81-e266-45cb-88f8-89595dece114}");
 const sinkContract = "@mozilla.org/network/unittest/channeleventsink;1";
 
@@ -111,13 +115,13 @@ function run_test() {
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/redirect", redirect);
   httpserv.registerPathHandler("/redirectfile", redirectfile);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   Components.manager.nsIComponentRegistrar.registerFactory(sinkCID,
     "Unit test Event sink", sinkContract, eventsink);
 
   // Step 1: Set the callbacks on the listener itself
-  var chan = makeChan("http://localhost:4444/redirect");
+  var chan = makeChan(URL + "/redirect");
   chan.notificationCallbacks = eventsink;
 
   chan.asyncOpen(listener, null);
@@ -136,13 +140,13 @@ function run_test_continued() {
     // Step 2: Category entry
     catMan.nsICategoryManager.addCategoryEntry(categoryName, "unit test",
                                                sinkContract, false, true);
-    chan = makeChan("http://localhost:4444/redirect")
+    chan = makeChan(URL + "/redirect")
   } else {
     // Step 3: Global contract id
     catMan.nsICategoryManager.deleteCategoryEntry(categoryName, "unit test",
                                                   false);
     listener.expectSinkCall = false;
-    chan = makeChan("http://localhost:4444/redirectfile");
+    chan = makeChan(URL + "/redirectfile");
   }
 
   listener._iteration++;
diff --git a/netwerk/test/unit/test_fallback_no-cache-entry_canceled.js b/netwerk/test/unit/test_fallback_no-cache-entry_canceled.js
index 801bd4a8882e..ee59348cb184 100644
--- a/netwerk/test/unit/test_fallback_no-cache-entry_canceled.js
+++ b/netwerk/test/unit/test_fallback_no-cache-entry_canceled.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -62,11 +65,11 @@ function run_test()
   httpServer.registerPathHandler("/masterEntry", masterEntryHandler);
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Components.classes["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -102,8 +105,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_no-cache-entry_passing.js b/netwerk/test/unit/test_fallback_no-cache-entry_passing.js
index 6e007c1e1353..4db64da16bce 100644
--- a/netwerk/test/unit/test_fallback_no-cache-entry_passing.js
+++ b/netwerk/test/unit/test_fallback_no-cache-entry_passing.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -62,11 +65,11 @@ function run_test()
   httpServer.registerPathHandler("/masterEntry", masterEntryHandler);
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Components.classes["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -101,8 +104,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_redirect-to-different-origin_canceled.js b/netwerk/test/unit/test_fallback_redirect-to-different-origin_canceled.js
index 4c3b1e5db8dd..7b431c9be43d 100644
--- a/netwerk/test/unit/test_fallback_redirect-to-different-origin_canceled.js
+++ b/netwerk/test/unit/test_fallback_redirect-to-different-origin_canceled.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -70,11 +73,11 @@ function run_test()
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
   httpServer.registerPathHandler(randomPath, redirectHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Cc["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -106,8 +109,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_redirect-to-different-origin_passing.js b/netwerk/test/unit/test_fallback_redirect-to-different-origin_passing.js
index 99fe44dc7dd0..161d0355c726 100644
--- a/netwerk/test/unit/test_fallback_redirect-to-different-origin_passing.js
+++ b/netwerk/test/unit/test_fallback_redirect-to-different-origin_passing.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -70,11 +73,11 @@ function run_test()
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
   httpServer.registerPathHandler(randomPath, redirectHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Cc["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -105,8 +108,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_request-error_canceled.js b/netwerk/test/unit/test_fallback_request-error_canceled.js
index f1b871a06df5..61f26c1b720f 100644
--- a/netwerk/test/unit/test_fallback_request-error_canceled.js
+++ b/netwerk/test/unit/test_fallback_request-error_canceled.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -69,11 +72,11 @@ function run_test()
   httpServer.registerPathHandler("/masterEntry", masterEntryHandler);
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Cc["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -92,6 +95,9 @@ function run_test()
   cacheUpdateObserver = {observe: function() {
     dump("got offline-cache-update-completed\n");
     // offline cache update completed.
+
+    // doing this to eval the lazy getter, otherwise the make_channel call would hang
+    randomURI;
     httpServer.stop(function() {
       // Now shut the server down to have an error in onStartRequest
       var chan = make_channel(randomURI);
@@ -109,8 +115,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_request-error_passing.js b/netwerk/test/unit/test_fallback_request-error_passing.js
index 13167c61782d..e9e63956ba8e 100644
--- a/netwerk/test/unit/test_fallback_request-error_passing.js
+++ b/netwerk/test/unit/test_fallback_request-error_passing.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -69,11 +72,11 @@ function run_test()
   httpServer.registerPathHandler("/masterEntry", masterEntryHandler);
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Cc["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -92,6 +95,7 @@ function run_test()
   cacheUpdateObserver = {observe: function() {
     dump("got offline-cache-update-completed\n");
     // offline cache update completed.
+    var _x = randomURI; // doing this so the lazy value gets computed
     httpServer.stop(function() {
       // Now shut the server down to have an error in onstartrequest
       var chan = make_channel(randomURI);
@@ -108,8 +112,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_response-error_canceled.js b/netwerk/test/unit/test_fallback_response-error_canceled.js
index e9cae33f970a..6b455eaf44cf 100644
--- a/netwerk/test/unit/test_fallback_response-error_canceled.js
+++ b/netwerk/test/unit/test_fallback_response-error_canceled.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/error/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -69,11 +72,11 @@ function run_test()
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
   httpServer.registerPathHandler(randomPath, errorHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Cc["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -105,8 +108,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_fallback_response-error_passing.js b/netwerk/test/unit/test_fallback_response-error_passing.js
index ffa765e75389..fd7ab7973f9e 100644
--- a/netwerk/test/unit/test_fallback_response-error_passing.js
+++ b/netwerk/test/unit/test_fallback_response-error_passing.js
@@ -8,7 +8,10 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/error/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + randomPath;
+});
 
 var cacheUpdateObserver = null;
 
@@ -69,11 +72,11 @@ function run_test()
   httpServer.registerPathHandler("/manifest", manifestHandler);
   httpServer.registerPathHandler("/content", contentHandler);
   httpServer.registerPathHandler(randomPath, errorHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var pm = Cc["@mozilla.org/permissionmanager;1"]
     .getService(Ci.nsIPermissionManager);
-  var uri = make_uri("http://localhost:4444");
+  var uri = make_uri("http://localhost:" + httpServer.identity.primaryPort);
   var principal = Cc["@mozilla.org/scriptsecuritymanager;1"]
                     .getService(Ci.nsIScriptSecurityManager)
                     .getNoAppCodebasePrincipal(uri);
@@ -104,8 +107,10 @@ function run_test()
 
   var us = Cc["@mozilla.org/offlinecacheupdate-service;1"].
            getService(Ci.nsIOfflineCacheUpdateService);
-  us.scheduleUpdate(make_uri("http://localhost:4444/manifest"),
-                    make_uri("http://localhost:4444/masterEntry"),
+  us.scheduleUpdate(make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/manifest"),
+                    make_uri("http://localhost:" +
+                             httpServer.identity.primaryPort + "/masterEntry"),
                     null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_force_sniffing.js b/netwerk/test/unit/test_force_sniffing.js
index 6ece79cd13ac..60d80649f3cf 100644
--- a/netwerk/test/unit/test_force_sniffing.js
+++ b/netwerk/test/unit/test_force_sniffing.js
@@ -67,14 +67,16 @@ function makeChan(url) {
   return chan;
 }
 
-var url = "http://localhost:4444/test";
+XPCOMUtils.defineLazyGetter(this, "url", function() {
+  return "http://localhost:" + httpserv.identity.primaryPort + "/test";
+});
 
 var httpserv = null;
 
 function run_test() {
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/test", handler);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   // Register our fake sniffer that always returns the content-type we want.
   Components.manager.nsIComponentRegistrar.registerFactory(snifferCID,
diff --git a/netwerk/test/unit/test_gzipped_206.js b/netwerk/test/unit/test_gzipped_206.js
index a0e9809f005c..4f073150792a 100644
--- a/netwerk/test/unit/test_gzipped_206.js
+++ b/netwerk/test/unit/test_gzipped_206.js
@@ -61,7 +61,8 @@ function cachedHandler(metadata, response) {
 
 function continue_test(request, data) {
   do_check_true(17 == data.length);
-  var chan = make_channel("http://localhost:4444/cached/test.gz");
+  var chan = make_channel("http://localhost:" +
+                          httpserver.identity.primaryPort + "/cached/test.gz");
   chan.asyncOpen(new ChannelListener(finish_test, null, CL_EXPECT_GZIP), null);
 }
 
@@ -77,12 +78,13 @@ function finish_test(request, data, ctx) {
 function run_test() {
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/cached/test.gz", cachedHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   // wipe out cached content
   evict_cache_entries();
 
-  var chan = make_channel("http://localhost:4444/cached/test.gz");
+  var chan = make_channel("http://localhost:" +
+                          httpserver.identity.primaryPort + "/cached/test.gz");
   chan.asyncOpen(new ChannelListener(continue_test, null, CL_EXPECT_GZIP), null);
   do_test_pending();
 }
diff --git a/netwerk/test/unit/test_head.js b/netwerk/test/unit/test_head.js
index 232c35dff1ee..98b5dd446102 100644
--- a/netwerk/test/unit/test_head.js
+++ b/netwerk/test/unit/test_head.js
@@ -10,6 +10,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var testpath = "/simple";
 var httpbody = "0123456789";
@@ -28,7 +32,7 @@ function setup_test() {
   if (dbg) { print("============== setup_test: in"); }
 
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   channel = setupChannel(testpath);
 
@@ -64,7 +68,7 @@ function setup_test() {
 
 function setupChannel(path) {
   ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + path, "", null);
+  var chan = ios.newChannel(URL + path, "", null);
   chan.QueryInterface(Ci.nsIHttpChannel);
   chan.requestMethod = "GET";
   return chan;
diff --git a/netwerk/test/unit/test_headers.js b/netwerk/test/unit/test_headers.js
index 9473e552d0d0..41b5243894ec 100644
--- a/netwerk/test/unit/test_headers.js
+++ b/netwerk/test/unit/test_headers.js
@@ -27,6 +27,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var index = 0;
 var nextTest = firstTest;
@@ -35,7 +39,7 @@ var testPathBase = "/test_headers";
 
 function run_test()
 {
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   do_test_pending();
   run_test_number(nextTest);
@@ -72,7 +76,7 @@ function setupChannel(url)
 {
   var ios = Components.classes["@mozilla.org/network/io-service;1"].
                        getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + url, "", null);
+  var chan = ios.newChannel(URL + url, "", null);
   var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
   return httpChan;
 }
diff --git a/netwerk/test/unit/test_httpcancel.js b/netwerk/test/unit/test_httpcancel.js
index b791f1e4b001..527e3666156c 100644
--- a/netwerk/test/unit/test_httpcancel.js
+++ b/netwerk/test/unit/test_httpcancel.js
@@ -90,7 +90,8 @@ function makeChan(url) {
 var httpserv = null;
 
 function execute_test() {
-  var chan = makeChan("http://localhost:4444/failtest");
+  var chan = makeChan("http://localhost:" +
+                      httpserv.identity.primaryPort + "/failtest");
 
   var obs = Components.classes["@mozilla.org/observer-service;1"].getService();
   obs = obs.QueryInterface(Components.interfaces.nsIObserverService);
@@ -102,7 +103,7 @@ function execute_test() {
 function run_test() {
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/failtest", failtest);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   execute_test();
 
diff --git a/netwerk/test/unit/test_httpsuspend.js b/netwerk/test/unit/test_httpsuspend.js
index 4ec513bf8c3e..e6267dfc1f1e 100644
--- a/netwerk/test/unit/test_httpsuspend.js
+++ b/netwerk/test/unit/test_httpsuspend.js
@@ -8,6 +8,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserv.identity.primaryPort;
+});
+
 const MIN_TIME_DIFFERENCE = 3000;
 const RESUME_DELAY = 5000;
 
@@ -65,9 +69,9 @@ var httpserv = null;
 function run_test() {
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/woo", data);
-  httpserv.start(4444);
+  httpserv.start(-1);
 
-  var chan = makeChan("http://localhost:4444/woo");
+  var chan = makeChan(URL + "/woo");
   chan.QueryInterface(Ci.nsIRequest);
   chan.asyncOpen(listener, null);
 
diff --git a/netwerk/test/unit/test_mismatch_last-modified.js b/netwerk/test/unit/test_mismatch_last-modified.js
index 6027e6474d40..acb85415e4e0 100644
--- a/netwerk/test/unit/test_mismatch_last-modified.js
+++ b/netwerk/test/unit/test_mismatch_last-modified.js
@@ -46,7 +46,8 @@ var listener_3 = {
     }
 };
 
-var listener_2 = {
+XPCOMUtils.defineLazyGetter(this, "listener_2", function() {
+    return {
     // this listener is used to process the revalidation of the
     // corrupted cache entry. its revalidation prompts it to be cleaned
 
@@ -73,12 +74,16 @@ var listener_2 = {
     onStopRequest: function test_onStopR(request, ctx, status) {
 	var channel = request.QueryInterface(Ci.nsIHttpChannel);
 
-	var chan = ios.newChannel("http://localhost:4444/test1", "", null);
+	var chan = ios.newChannel("http://localhost:" +
+				  httpserver.identity.primaryPort +
+				  "/test1", "", null);
 	chan.asyncOpen(listener_3, null);
     }
 };
+});
 
-var listener_1 = {
+XPCOMUtils.defineLazyGetter(this, "listener_1", function() {
+    return {
     // this listener processes the initial request from a empty cache.
     // the server responds with the wrong data ('A')
 
@@ -101,10 +106,13 @@ var listener_1 = {
     onStopRequest: function test_onStopR(request, ctx, status) {
 	var channel = request.QueryInterface(Ci.nsIHttpChannel);
 
-	var chan = ios.newChannel("http://localhost:4444/test1", "", null);
+	var chan = ios.newChannel("http://localhost:" +
+				  httpserver.identity.primaryPort +
+				  "/test1", "", null);
 	chan.asyncOpen(listener_2, null);
     }
 };
+});
 
 function run_test() {
     do_get_profile();
@@ -114,9 +122,11 @@ function run_test() {
     evict_cache_entries();
 
     httpserver.registerPathHandler("/test1", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
-    var chan = ios.newChannel("http://localhost:4444/test1", "", null);
+    var port = httpserver.identity.primaryPort;
+
+    var chan = ios.newChannel("http://localhost:" + port + "/test1", "", null);
     chan.asyncOpen(listener_1, null);
 
     do_test_pending();
diff --git a/netwerk/test/unit/test_multipart_byteranges.js b/netwerk/test/unit/test_multipart_byteranges.js
index bb4172dfc97f..c34b14b1936e 100644
--- a/netwerk/test/unit/test_multipart_byteranges.js
+++ b/netwerk/test/unit/test_multipart_byteranges.js
@@ -6,7 +6,10 @@ const Cr = Components.results;
 Cu.import("resource://testing-common/httpd.js");
 
 var httpserver = null;
-var uri = "http://localhost:4444/multipart";
+
+XPCOMUtils.defineLazyGetter(this, "uri", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + "/multipart";
+});
 
 function make_channel(url) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -107,7 +110,7 @@ function run_test()
 {
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/multipart", contentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var streamConv = Cc["@mozilla.org/streamConverters;1"]
                      .getService(Ci.nsIStreamConverterService);
diff --git a/netwerk/test/unit/test_multipart_streamconv.js b/netwerk/test/unit/test_multipart_streamconv.js
index 7b83eec4b59a..5e0d52304dff 100644
--- a/netwerk/test/unit/test_multipart_streamconv.js
+++ b/netwerk/test/unit/test_multipart_streamconv.js
@@ -6,7 +6,10 @@ const Cr = Components.results;
 Cu.import("resource://testing-common/httpd.js");
 
 var httpserver = null;
-var uri = "http://localhost:4444/multipart";
+
+XPCOMUtils.defineLazyGetter(this, "uri", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + "/multipart";
+});
 
 function make_channel(url) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -83,7 +86,7 @@ function run_test()
 {
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/multipart", contentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var streamConv = Cc["@mozilla.org/streamConverters;1"]
                      .getService(Ci.nsIStreamConverterService);
diff --git a/netwerk/test/unit/test_multipart_streamconv_missing_lead_boundary.js b/netwerk/test/unit/test_multipart_streamconv_missing_lead_boundary.js
index 32170e4be069..bf78d13f6894 100644
--- a/netwerk/test/unit/test_multipart_streamconv_missing_lead_boundary.js
+++ b/netwerk/test/unit/test_multipart_streamconv_missing_lead_boundary.js
@@ -6,7 +6,10 @@ const Cr = Components.results;
 Cu.import("resource://testing-common/httpd.js");
 
 var httpserver = null;
-var uri = "http://localhost:4444/multipart";
+
+XPCOMUtils.defineLazyGetter(this, "uri", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort + "/multipart";
+});
 
 function make_channel(url) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -83,7 +86,7 @@ function run_test()
 {
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/multipart", contentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var streamConv = Cc["@mozilla.org/streamConverters;1"]
                      .getService(Ci.nsIStreamConverterService);
diff --git a/netwerk/test/unit/test_nojsredir.js b/netwerk/test/unit/test_nojsredir.js
index 5de0bd639386..a39f2192b588 100644
--- a/netwerk/test/unit/test_nojsredir.js
+++ b/netwerk/test/unit/test_nojsredir.js
@@ -22,7 +22,8 @@ var tests = [
 function setupChannel(url) {
     var ios = Components.classes["@mozilla.org/network/io-service;1"].
                          getService(Ci.nsIIOService);
-    var chan = ios.newChannel("http://localhost:4444" + url, "", null);
+    var chan = ios.newChannel("http://localhost:" +
+			      httpserver.identity.primaryPort + url, "", null);
     return chan;
 }
 
@@ -42,7 +43,7 @@ function completeIter(request, data, ctx) {
 
 function run_test() {
     httpserver.registerPathHandler("/test/test", handler);
-    httpserver.start(4444);
+    httpserver.start(-1);
 
     startIter();
     do_test_pending();
diff --git a/netwerk/test/unit/test_pinned_app_cache.js b/netwerk/test/unit/test_pinned_app_cache.js
index 7c9fb6d01515..74a0a79a1e28 100644
--- a/netwerk/test/unit/test_pinned_app_cache.js
+++ b/netwerk/test/unit/test_pinned_app_cache.js
@@ -57,8 +57,14 @@ const kManifest2 = "CACHE MANIFEST\n" +
 
 const kDataFileSize = 1024;	// file size for each content page
 const kCacheSize = kDataFileSize * 5; // total space for offline cache storage
-const kHttpLocation = "http://localhost:4444/";
-const kHttpLocation_ip = "http://127.0.0.1:4444/";
+
+XPCOMUtils.defineLazyGetter(this, "kHttpLocation", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + "/";
+});
+
+XPCOMUtils.defineLazyGetter(this, "kHttpLocation_ip", function() {
+  return "http://127.0.0.1:" + httpServer.identity.primaryPort + "/";
+});
 
 function manifest1_handler(metadata, response) {
   do_print("manifest1\n");
@@ -113,7 +119,7 @@ function init_http_server() {
   for (i = 1; i <= 8; i++) {
     httpServer.registerPathHandler("/pages/foo" + i, datafile_handler);
   }
-  httpServer.start(4444);
+  httpServer.start(-1);
 }
 
 function init_cache_capacity() {
diff --git a/netwerk/test/unit/test_plaintext_sniff.js b/netwerk/test/unit/test_plaintext_sniff.js
index 0cedfaff15f7..10c2ebbd319e 100644
--- a/netwerk/test/unit/test_plaintext_sniff.js
+++ b/netwerk/test/unit/test_plaintext_sniff.js
@@ -81,8 +81,8 @@ function makeChan(headerIdx, bodyIdx) {
   var ios = Components.classes["@mozilla.org/network/io-service;1"]
                       .getService(Components.interfaces.nsIIOService);
   var chan =
-    ios.newChannel("http://localhost:4444/" + headerIdx + "/" + bodyIdx, null,
-                   null)
+    ios.newChannel("http://localhost:" + httpserv.identity.primaryPort +
+                   "/" + headerIdx + "/" + bodyIdx, null, null)
        .QueryInterface(Components.interfaces.nsIHttpChannel);
 
   chan.loadFlags |=
@@ -193,7 +193,7 @@ function run_test() {
     }
   }
 
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   doTest(0, 0);
 }
diff --git a/netwerk/test/unit/test_post.js b/netwerk/test/unit/test_post.js
index 7e82bf87196d..a403df16a912 100644
--- a/netwerk/test/unit/test_post.js
+++ b/netwerk/test/unit/test_post.js
@@ -9,6 +9,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var testpath = "/simple";
 
@@ -56,7 +60,7 @@ function run_test() {
   mime.addContentLength = true;
 
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var channel = setupChannel(testpath);
 
@@ -71,7 +75,7 @@ function run_test() {
 
 function setupChannel(path) {
   var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  return chan = ios.newChannel("http://localhost:4444" + path, "", null)
+  return chan = ios.newChannel(URL + path, "", null)
                    .QueryInterface(Ci.nsIHttpChannel);
 }
 
diff --git a/netwerk/test/unit/test_private_necko_channel.js b/netwerk/test/unit/test_private_necko_channel.js
index 732b61051ae5..056b630c9b3b 100644
--- a/netwerk/test/unit/test_private_necko_channel.js
+++ b/netwerk/test/unit/test_private_necko_channel.js
@@ -21,7 +21,7 @@ function run_test() {
   evict_cache_entries();
 
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var channel = setupChannel(testpath);
   channel.loadGroup = Cc["@mozilla.org/network/load-group;1"].createInstance();
@@ -36,7 +36,8 @@ function run_test() {
 
 function setupChannel(path) {
   var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
-  return chan = ios.newChannel("http://localhost:4444" + path, "", null)
+  return chan = ios.newChannel("http://localhost:" +
+                               httpserver.identity.primaryPort + path, "", null)
                    .QueryInterface(Ci.nsIHttpChannel);
 }
 
diff --git a/netwerk/test/unit/test_progress.js b/netwerk/test/unit/test_progress.js
index c469fa85774d..2fea9d426aa7 100644
--- a/netwerk/test/unit/test_progress.js
+++ b/netwerk/test/unit/test_progress.js
@@ -5,6 +5,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var testpath = "/simple";
 var httpbody = "0123456789";
@@ -98,7 +102,7 @@ var progressCallback = {
 
 function run_test() {
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
   var channel = setupChannel(testpath);
   channel.asyncOpen(progressCallback, null);
   do_test_pending();
@@ -107,7 +111,7 @@ function run_test() {
 function setupChannel(path) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
                        getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + path, "", null);
+  var chan = ios.newChannel(URL + path, "", null);
   chan.QueryInterface(Ci.nsIHttpChannel);
   chan.requestMethod = "GET";
   chan.notificationCallbacks = progressCallback;
diff --git a/netwerk/test/unit/test_proxy-failover_canceled.js b/netwerk/test/unit/test_proxy-failover_canceled.js
index 24a8c73a4d4b..f54f200068d7 100644
--- a/netwerk/test/unit/test_proxy-failover_canceled.js
+++ b/netwerk/test/unit/test_proxy-failover_canceled.js
@@ -31,7 +31,7 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   // we want to cancel the failover proxy engage, so, do not allow
   // redirects from now.
@@ -44,10 +44,12 @@ function run_test()
   var prefs = prefserv.getBranch("network.proxy.");
   prefs.setIntPref("type", 2);
   prefs.setCharPref("autoconfig_url", "data:text/plain," +
-    "function FindProxyForURL(url, host) {return 'PROXY a_non_existent_domain_x7x6c572v:80; PROXY localhost:4444';}"
+    "function FindProxyForURL(url, host) {return 'PROXY a_non_existent_domain_x7x6c572v:80; PROXY localhost:" +
+    httpServer.identity.primaryPort + "';}"
   );
 
-  var chan = make_channel("http://localhost:4444/content");
+  var chan = make_channel("http://localhost:" +
+                          httpServer.identity.primaryPort + "/content");
   chan.notificationCallbacks = nc;
   chan.asyncOpen(new ChannelListener(finish_test, null, CL_EXPECT_FAILURE), null);
   do_test_pending();
diff --git a/netwerk/test/unit/test_proxy-failover_passing.js b/netwerk/test/unit/test_proxy-failover_passing.js
index 045379c8b3b0..b2c4304b5d98 100644
--- a/netwerk/test/unit/test_proxy-failover_passing.js
+++ b/netwerk/test/unit/test_proxy-failover_passing.js
@@ -31,17 +31,19 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var prefserv = Cc["@mozilla.org/preferences-service;1"].
                  getService(Ci.nsIPrefService);
   var prefs = prefserv.getBranch("network.proxy.");
   prefs.setIntPref("type", 2);
   prefs.setCharPref("autoconfig_url", "data:text/plain," +
-    "function FindProxyForURL(url, host) {return 'PROXY a_non_existent_domain_x7x6c572v:80; PROXY localhost:4444';}"
+    "function FindProxyForURL(url, host) {return 'PROXY a_non_existent_domain_x7x6c572v:80; PROXY localhost:" +
+    httpServer.identity.primaryPort + "';}"
   );
 
-  var chan = make_channel("http://localhost:4444/content");
+  var chan = make_channel("http://localhost:" +
+                          httpServer.identity.primaryPort + "/content");
   chan.asyncOpen(new ChannelListener(finish_test, null), null);
   do_test_pending();
 }
diff --git a/netwerk/test/unit/test_proxy-replace_canceled.js b/netwerk/test/unit/test_proxy-replace_canceled.js
index bafb57d0c5c7..361320232e41 100644
--- a/netwerk/test/unit/test_proxy-replace_canceled.js
+++ b/netwerk/test/unit/test_proxy-replace_canceled.js
@@ -31,14 +31,15 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var prefserv = Cc["@mozilla.org/preferences-service;1"].
                  getService(Ci.nsIPrefService);
   var prefs = prefserv.getBranch("network.proxy.");
   prefs.setIntPref("type", 2);
   prefs.setCharPref("autoconfig_url", "data:text/plain," +
-    "function FindProxyForURL(url, host) {return 'PROXY localhost:4444';}"
+    "function FindProxyForURL(url, host) {return 'PROXY localhost:" +
+    httpServer.identity.primaryPort + "';}"
   );
 
   // this test assumed that a AsyncOnChannelRedirect query is made for
@@ -49,7 +50,8 @@ function run_test()
   // internal redirect used to setup the initial proxy/channel as that isn't
   // a redirect in any sense.
 
-  var chan = make_channel("http://localhost:4444/content");
+  var chan = make_channel("http://localhost:" +
+                          httpServer.identity.primaryPort + "/content");
   chan.asyncOpen(new ChannelListener(finish_test, null, CL_EXPECT_FAILURE), null);
   chan.cancel(Cr.NS_BINDING_ABORTED);
   do_test_pending();
diff --git a/netwerk/test/unit/test_proxy-replace_passing.js b/netwerk/test/unit/test_proxy-replace_passing.js
index a39af749bd92..7c8e01f98604 100644
--- a/netwerk/test/unit/test_proxy-replace_passing.js
+++ b/netwerk/test/unit/test_proxy-replace_passing.js
@@ -31,17 +31,19 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var prefserv = Cc["@mozilla.org/preferences-service;1"].
                  getService(Ci.nsIPrefService);
   var prefs = prefserv.getBranch("network.proxy.");
   prefs.setIntPref("type", 2);
   prefs.setCharPref("autoconfig_url", "data:text/plain," +
-    "function FindProxyForURL(url, host) {return 'PROXY localhost:4444';}"
+    "function FindProxyForURL(url, host) {return 'PROXY localhost:" +
+    httpServer.identity.primaryPort + "';}"
   );
 
-  var chan = make_channel("http://localhost:4444/content");
+  var chan = make_channel("http://localhost:" +
+                          httpServer.identity.primaryPort + "/content");
   chan.asyncOpen(new ChannelListener(finish_test, null), null);
   do_test_pending();
 }
diff --git a/netwerk/test/unit/test_range_requests.js b/netwerk/test/unit/test_range_requests.js
index 6015766ddd15..5cb51183d926 100644
--- a/netwerk/test/unit/test_range_requests.js
+++ b/netwerk/test/unit/test_range_requests.js
@@ -33,6 +33,7 @@ const decodedBody = [0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x61, 0x20,
                      0x6c, 0x79, 0x20, 0x6c, 0x6f, 0x6e, 0x67, 0x65, 0x72, 0x20, 0x74, 0x65, 0x73, 0x74, 0x0a, 0x0a];
 
 const partial_data_length = 4;
+var port = null; // set in run_test
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -107,7 +108,7 @@ function handler_2(metadata, response) {
 }
 function received_partial_2(request, data) {
   do_check_eq(data, undefined);
-  var chan = make_channel("http://localhost:4444/test_2");
+  var chan = make_channel("http://localhost:" + port + "/test_2");
   chan.asyncOpen(new ChannelListener(received_cleartext, null), null);
 }
 
@@ -135,7 +136,7 @@ function handler_3(metadata, response) {
 }
 function received_partial_3(request, data) {
   do_check_eq(partial_data_length, data.length);
-  var chan = make_channel("http://localhost:4444/test_3");
+  var chan = make_channel("http://localhost:" + port + "/test_3");
   chan.asyncOpen(new ChannelListener(received_cleartext, null), null);
 }
 
@@ -168,7 +169,7 @@ function handler_4(metadata, response) {
 function received_partial_4(request, data) {
 // checking length does not work with encoded data
 //  do_check_eq(partial_data_length, data.length);
-  var chan = make_channel("http://localhost:4444/test_4");
+  var chan = make_channel("http://localhost:" + port + "/test_4");
   chan.asyncOpen(new MyListener(received_cleartext), null);
 }
 
@@ -195,7 +196,7 @@ function handler_5(metadata, response) {
 }
 function received_partial_5(request, data) {
   do_check_eq(partial_data_length, data.length);
-  var chan = make_channel("http://localhost:4444/test_5");
+  var chan = make_channel("http://localhost:" + port + "/test_5");
   chan.setRequestHeader("If-Match", "Some eTag", false);
   chan.asyncOpen(new ChannelListener(received_cleartext, null), null);
 }
@@ -226,7 +227,7 @@ function handler_6(metadata, response) {
 function received_partial_6(request, data) {
 // would like to verify that the response does not have Accept-Ranges
   do_check_eq(partial_data_length, data.length);
-  var chan = make_channel("http://localhost:4444/test_6");
+  var chan = make_channel("http://localhost:" + port + "/test_6");
   chan.asyncOpen(new ChannelListener(received_cleartext, null), null);
 }
 
@@ -244,29 +245,31 @@ function run_test() {
   httpserver.registerPathHandler("/test_4", handler_4);
   httpserver.registerPathHandler("/test_5", handler_5);
   httpserver.registerPathHandler("/test_6", handler_6);
-  httpserver.start(4444);
+  httpserver.start(-1);
+
+  port = httpserver.identity.primaryPort;
 
   // wipe out cached content
   evict_cache_entries();
 
   // Case 2: zero-length partial entry must not trigger range-request
-  var chan = make_channel("http://localhost:4444/test_2");
+  var chan = make_channel("http://localhost:" + port + "/test_2");
   chan.asyncOpen(new Canceler(received_partial_2), null);
 
   // Case 3: no-store response must not trigger range-request
-  var chan = make_channel("http://localhost:4444/test_3");
+  var chan = make_channel("http://localhost:" + port + "/test_3");
   chan.asyncOpen(new MyListener(received_partial_3), null);
 
   // Case 4: response with content-encoding must not trigger range-request
-  var chan = make_channel("http://localhost:4444/test_4");
+  var chan = make_channel("http://localhost:" + port + "/test_4");
   chan.asyncOpen(new MyListener(received_partial_4), null);
 
   // Case 5: conditional request-header set by client
-  var chan = make_channel("http://localhost:4444/test_5");
+  var chan = make_channel("http://localhost:" + port + "/test_5");
   chan.asyncOpen(new MyListener(received_partial_5), null);
 
   // Case 6: response is not resumable (drop the Accept-Ranges header)
-  var chan = make_channel("http://localhost:4444/test_6");
+  var chan = make_channel("http://localhost:" + port + "/test_6");
   chan.asyncOpen(new MyListener(received_partial_6), null);
 
   do_test_pending();
diff --git a/netwerk/test/unit/test_redirect-caching_canceled.js b/netwerk/test/unit/test_redirect-caching_canceled.js
index f3d281631c99..374d99a4bff9 100644
--- a/netwerk/test/unit/test_redirect-caching_canceled.js
+++ b/netwerk/test/unit/test_redirect-caching_canceled.js
@@ -5,10 +5,17 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return URL + randomPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -21,7 +28,7 @@ const responseBody = "response body";
 function redirectHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "http://localhost:4444/content", false);
+  response.setHeader("Location", URL + "/content", false);
   response.setHeader("Cache-control", "max-age=1000", false);
   return;
 }
@@ -59,7 +66,7 @@ function run_test()
   httpServer = new HttpServer();
   httpServer.registerPathHandler(randomPath, redirectHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var chan = make_channel(randomURI);
   chan.asyncOpen(new ChannelListener(firstTimeThrough, null), null);
diff --git a/netwerk/test/unit/test_redirect-caching_failure.js b/netwerk/test/unit/test_redirect-caching_failure.js
index e64aa6859910..7525ab4301d2 100644
--- a/netwerk/test/unit/test_redirect-caching_failure.js
+++ b/netwerk/test/unit/test_redirect-caching_failure.js
@@ -5,10 +5,17 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return URL + randomPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -19,7 +26,8 @@ function make_channel(url, callback, ctx) {
 function redirectHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "httpx://localhost:4444/content", false);
+  response.setHeader("Location", "httpx://localhost:" +
+                     httpServer.identity.primaryPort + "/content", false);
   response.setHeader("Cache-control", "max-age=1000", false);
 }
 
@@ -45,7 +53,7 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler(randomPath, redirectHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var chan = make_channel(randomURI);
   chan.asyncOpen(new ChannelListener(makeSureNotInCache, null, CL_EXPECT_FAILURE), null);
diff --git a/netwerk/test/unit/test_redirect-caching_passing.js b/netwerk/test/unit/test_redirect-caching_passing.js
index 8d72601a7983..3d6c4a6cf70d 100644
--- a/netwerk/test/unit/test_redirect-caching_passing.js
+++ b/netwerk/test/unit/test_redirect-caching_passing.js
@@ -5,10 +5,17 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return URL + randomPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -21,7 +28,7 @@ const responseBody = "response body";
 function redirectHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "http://localhost:4444/content", false);
+  response.setHeader("Location", URL + "/content", false);
   return;
 }
 
@@ -50,7 +57,7 @@ function run_test()
   httpserver = new HttpServer();
   httpserver.registerPathHandler(randomPath, redirectHandler);
   httpserver.registerPathHandler("/content", contentHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   var chan = make_channel(randomURI);
   chan.asyncOpen(new ChannelListener(firstTimeThrough, null), null);
diff --git a/netwerk/test/unit/test_redirect_baduri.js b/netwerk/test/unit/test_redirect_baduri.js
index d6dd2b3dec23..90c2629e1edd 100644
--- a/netwerk/test/unit/test_redirect_baduri.js
+++ b/netwerk/test/unit/test_redirect_baduri.js
@@ -12,7 +12,9 @@ Cu.import("resource://testing-common/httpd.js");
 var httpServer = null;
 
 var BadRedirectPath = "/BadRedirect";
-var BadRedirectURI = "http://localhost:4444" + BadRedirectPath;
+XPCOMUtils.defineLazyGetter(this, "BadRedirectURI", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort + BadRedirectPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -38,7 +40,7 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler(BadRedirectPath, BadRedirectHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var chan = make_channel(BadRedirectURI);
   chan.asyncOpen(new ChannelListener(checkFailed, null, CL_EXPECT_FAILURE),
diff --git a/netwerk/test/unit/test_redirect_canceled.js b/netwerk/test/unit/test_redirect_canceled.js
index e4839288ed29..f36641b4d3ea 100644
--- a/netwerk/test/unit/test_redirect_canceled.js
+++ b/netwerk/test/unit/test_redirect_canceled.js
@@ -5,10 +5,17 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return URL + randomPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -21,7 +28,7 @@ const responseBody = "response body";
 function redirectHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "http://localhost:4444/content", false);
+  response.setHeader("Location", URL + "/content", false);
 }
 
 function contentHandler(metadata, response)
@@ -41,7 +48,7 @@ function run_test()
   httpServer = new HttpServer();
   httpServer.registerPathHandler(randomPath, redirectHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var chan = make_channel(randomURI);
   chan.notificationCallbacks = new ChannelEventSink(ES_ABORT_REDIRECT);
diff --git a/netwerk/test/unit/test_redirect_failure.js b/netwerk/test/unit/test_redirect_failure.js
index 09156a48173b..6fb33694897b 100644
--- a/netwerk/test/unit/test_redirect_failure.js
+++ b/netwerk/test/unit/test_redirect_failure.js
@@ -5,10 +5,17 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return URL + randomPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -19,7 +26,8 @@ function make_channel(url, callback, ctx) {
 function redirectHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "httpx://localhost:4444/content", false);
+  response.setHeader("Location", "httpx://localhost:" +
+                     httpServer.identity.primaryPort + "/content", false);
   response.setHeader("Cache-Control", "no-cache", false);
 }
 
@@ -35,7 +43,7 @@ function run_test()
 {
   httpServer = new HttpServer();
   httpServer.registerPathHandler(randomPath, redirectHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var chan = make_channel(randomURI);
   chan.asyncOpen(new ChannelListener(finish_test, null, CL_EXPECT_FAILURE), null);
diff --git a/netwerk/test/unit/test_redirect_from_script.js b/netwerk/test/unit/test_redirect_from_script.js
index 4d0c25e53bff..20fe0812537c 100644
--- a/netwerk/test/unit/test_redirect_from_script.js
+++ b/netwerk/test/unit/test_redirect_from_script.js
@@ -36,31 +36,52 @@ redirectHook = "http-on-modify-request";
 
 var httpServer = null, httpServer2 = null;
 
+XPCOMUtils.defineLazyGetter(this, "port1", function() {
+  return httpServer.identity.primaryPort;
+});
+
+XPCOMUtils.defineLazyGetter(this, "port2", function() {
+  return httpServer2.identity.primaryPort;
+});
+
 // Test Part 1: a cross-path redirect on a single HTTP server
-// http://localhost:4444/bait -> http://localhost:4444/switch
+// http://localhost:port1/bait -> http://localhost:port1/switch
 var baitPath = "/bait";
-var baitURI = "http://localhost:4444" + baitPath;
+XPCOMUtils.defineLazyGetter(this, "baitURI", function() {
+  return "http://localhost:" + port1 + baitPath;
+});
 var baitText = "you got the worm";
 
 var redirectedPath = "/switch";
-var redirectedURI = "http://localhost:4444" + redirectedPath;
+XPCOMUtils.defineLazyGetter(this, "redirectedURI", function() {
+  return "http://localhost:" + port1 + redirectedPath;
+});
 var redirectedText = "worms are not tasty";
 
 // Test Part 2: Now, a redirect to a different server
-// http://localhost:4444/bait2 -> http://localhost:4445/switch
+// http://localhost:port1/bait2 -> http://localhost:port2/switch
 var bait2Path = "/bait2";
-var bait2URI = "http://localhost:4444" + bait2Path;
-var redirected2URI = "http://localhost:4445" + redirectedPath;
+XPCOMUtils.defineLazyGetter(this, "bait2URI", function() {
+  return "http://localhost:" + port1 + bait2Path;
+});
+
+XPCOMUtils.defineLazyGetter(this, "redirected2URI", function() {
+  return "http://localhost:" + port2 + redirectedPath;
+});
 
 // Test Part 3, begin with a serverside redirect that itself turns into an instance
 // of Test Part 1
 var bait3Path = "/bait3";
-var bait3URI = "http://localhost:4444" + bait3Path;
+XPCOMUtils.defineLazyGetter(this, "bait3URI", function() {
+  return "http://localhost:" + port1 + bait3Path;
+});
 
 // Test Part 4, begin with this client-side redirect and which then redirects
 // to an instance of Test Part 1
 var bait4Path = "/bait4";
-var bait4URI = "http://localhost:4444" + bait4Path;
+XPCOMUtils.defineLazyGetter(this, "bait4URI", function() {
+  return "http://localhost:" + port1 + bait4Path;
+});
 
 var testHeaderName = "X-Redirected-By-Script"
 var testHeaderVal = "Success";
@@ -175,15 +196,12 @@ function makeAsyncTest(uri, headerValue, nextTask)
   return test;
 }
 
-
-// The tests depend on each other, and therefore need to be defined in the
-// reverse of the order they are called in.  It is therefore best to read this
-// stanza backwards!
-
-var testViaAsyncOpen4 = makeAsyncTest(bait4URI, testHeaderVal, done);
-var testViaAsyncOpen3 = makeAsyncTest(bait3URI, testHeaderVal, testViaAsyncOpen4);
-var testViaAsyncOpen2 = makeAsyncTest(bait2URI, testHeaderVal2, testViaAsyncOpen3);
-var testViaAsyncOpen  = makeAsyncTest(baitURI,  testHeaderVal, testViaAsyncOpen2);
+// will be defined in run_test because of the lazy getters,
+// since the server's port is defined dynamically
+var testViaAsyncOpen4 = null;
+var testViaAsyncOpen3 = null;
+var testViaAsyncOpen2 = null;
+var testViaAsyncOpen  = null;
 
 function testViaXHR()
 {
@@ -226,10 +244,18 @@ function run_test()
   httpServer.registerPathHandler(bait3Path, bait3Handler);
   httpServer.registerPathHandler(bait4Path, baitHandler);
   httpServer.registerPathHandler(redirectedPath, redirectedHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer2 = new HttpServer();
   httpServer2.registerPathHandler(redirectedPath, redirected2Handler);
-  httpServer2.start(4445);
+  httpServer2.start(-1);
+
+  // The tests depend on each other, and therefore need to be defined in the
+  // reverse of the order they are called in.  It is therefore best to read this
+  // stanza backwards!
+  testViaAsyncOpen4 = makeAsyncTest(bait4URI, testHeaderVal, done);
+  testViaAsyncOpen3 = makeAsyncTest(bait3URI, testHeaderVal, testViaAsyncOpen4);
+  testViaAsyncOpen2 = makeAsyncTest(bait2URI, testHeaderVal2, testViaAsyncOpen3);
+  testViaAsyncOpen  = makeAsyncTest(baitURI,  testHeaderVal, testViaAsyncOpen2);
 
   testViaXHR();
   testViaAsyncOpen();  // will call done() asynchronously for cleanup
diff --git a/netwerk/test/unit/test_redirect_loop.js b/netwerk/test/unit/test_redirect_loop.js
index 2028c2d8f43c..2343c6bc23c0 100644
--- a/netwerk/test/unit/test_redirect_loop.js
+++ b/netwerk/test/unit/test_redirect_loop.js
@@ -12,17 +12,19 @@ Cu.import("resource://testing-common/httpd.js");
  * URI when the original URI ends in a slash).
  */
 
-var httpServer = null;
+var httpServer = new HttpServer();
+httpServer.start(-1);
+const PORT = httpServer.identity.primaryPort;
 
 var fullLoopPath = "/fullLoop"; 
-var fullLoopURI = "http://localhost:4444" + fullLoopPath;
+var fullLoopURI = "http://localhost:" + PORT + fullLoopPath;
 
 var relativeLoopPath = "/relativeLoop"; 
-var relativeLoopURI = "http://localhost:4444" + relativeLoopPath;
+var relativeLoopURI = "http://localhost:" + PORT + relativeLoopPath;
 
 // must use directory-style URI, so empty Location redirects back to self
 var emptyLoopPath = "/empty/";
-var emptyLoopURI = "http://localhost:4444" + emptyLoopPath;
+var emptyLoopURI = "http://localhost:" + PORT + emptyLoopPath;
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -33,7 +35,7 @@ function make_channel(url, callback, ctx) {
 function fullLoopHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "http://localhost:4444/fullLoop", false);
+  response.setHeader("Location", "http://localhost:" + PORT + "/fullLoop", false);
 }
 
 function relativeLoopHandler(metadata, response)
@@ -82,11 +84,9 @@ function testEmptyLoop(request, buffer)
 
 function run_test()
 {
-  httpServer = new HttpServer();
   httpServer.registerPathHandler(fullLoopPath, fullLoopHandler);
   httpServer.registerPathHandler(relativeLoopPath, relativeLoopHandler);
   httpServer.registerPathHandler(emptyLoopPath, emptyLoopHandler);
-  httpServer.start(4444);
 
   var chan = make_channel(fullLoopURI);
   chan.asyncOpen(new ChannelListener(testFullLoop, null, CL_EXPECT_FAILURE),
diff --git a/netwerk/test/unit/test_redirect_passing.js b/netwerk/test/unit/test_redirect_passing.js
index 823e51ed93cb..21ffb86cd2c0 100644
--- a/netwerk/test/unit/test_redirect_passing.js
+++ b/netwerk/test/unit/test_redirect_passing.js
@@ -5,10 +5,17 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
 var httpServer = null;
 // Need to randomize, because apparently no one clears our cache
 var randomPath = "/redirect/" + Math.random();
-var randomURI = "http://localhost:4444" + randomPath;
+
+XPCOMUtils.defineLazyGetter(this, "randomURI", function() {
+  return URL + randomPath;
+});
 
 function make_channel(url, callback, ctx) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
@@ -21,7 +28,7 @@ const responseBody = "response body";
 function redirectHandler(metadata, response)
 {
   response.setStatusLine(metadata.httpVersion, 301, "Moved");
-  response.setHeader("Location", "http://localhost:4444/content", false);
+  response.setHeader("Location", URL + "/content", false);
 }
 
 function contentHandler(metadata, response)
@@ -48,7 +55,7 @@ function run_test()
   httpServer = new HttpServer();
   httpServer.registerPathHandler(randomPath, redirectHandler);
   httpServer.registerPathHandler("/content", contentHandler);
-  httpServer.start(4444);
+  httpServer.start(-1);
 
   var chan = make_channel(randomURI);
   chan.asyncOpen(new ChannelListener(firstTimeThrough, null), null);
diff --git a/netwerk/test/unit/test_reentrancy.js b/netwerk/test/unit/test_reentrancy.js
index 75fa5c486ab7..85198602d23b 100644
--- a/netwerk/test/unit/test_reentrancy.js
+++ b/netwerk/test/unit/test_reentrancy.js
@@ -5,6 +5,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = new HttpServer();
 var testpath = "/simple";
 var httpbody = "<?xml version='1.0' ?><root>0123456789</root>";
@@ -13,7 +17,7 @@ function syncXHR()
 {
   var xhr = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"]
             .createInstance(Ci.nsIXMLHttpRequest);
-  xhr.open("GET", "http://localhost:4444" + testpath, false);
+  xhr.open("GET", URL + testpath, false);
   xhr.send(null);    
 }
 
@@ -84,7 +88,7 @@ function makeChan(url) {
 
 function next_test()
 {
-  var chan = makeChan("http://localhost:4444" + testpath);
+  var chan = makeChan(URL + testpath);
   chan.QueryInterface(Ci.nsIRequest);
   chan.asyncOpen(listener, null);
 }
@@ -92,7 +96,7 @@ function next_test()
 function run_test()
 {
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   next_test();
 
diff --git a/netwerk/test/unit/test_reopen.js b/netwerk/test/unit/test_reopen.js
index 9baff5d17bbd..6305eaaa6f5b 100644
--- a/netwerk/test/unit/test_reopen.js
+++ b/netwerk/test/unit/test_reopen.js
@@ -113,7 +113,7 @@ function test_data_channel() {
 
 function test_http_channel() {
   test_channel(function() {
-    return makeChan("http://localhost:4444/");
+    return makeChan("http://localhost:" + httpserv.identity.primaryPort + "/");
   });
 }
 
@@ -138,7 +138,7 @@ function end() {
 function run_test() {
   // start server
   httpserv = new HttpServer();
-  httpserv.start(4444);
+  httpserv.start(-1);
 
   run_next_test();
 }
diff --git a/netwerk/test/unit/test_resumable_channel.js b/netwerk/test/unit/test_resumable_channel.js
index 2eda347f57c2..e448a896cff7 100644
--- a/netwerk/test/unit/test_resumable_channel.js
+++ b/netwerk/test/unit/test_resumable_channel.js
@@ -7,6 +7,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpserver.identity.primaryPort;
+});
+
 var httpserver = null;
 
 const NS_ERROR_ENTITY_CHANGED = 0x804b0020;
@@ -90,7 +94,7 @@ function run_test() {
     dump("*** entity id = " + entityID + "\n");
 
     // Try a non-resumable URL (responds with 200)
-    var chan = make_channel("http://localhost:4444/");
+    var chan = make_channel(URL);
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.asyncOpen(new ChannelListener(try_resume, null, CL_EXPECT_FAILURE), null);
   }
@@ -100,7 +104,7 @@ function run_test() {
     do_check_eq(request.status, NS_ERROR_NOT_RESUMABLE);
 
     // Try a successful resume
-    var chan = make_channel("http://localhost:4444/range");
+    var chan = make_channel(URL + "/range");
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.asyncOpen(new ChannelListener(try_resume_zero, null), null);
   }
@@ -111,7 +115,7 @@ function run_test() {
     do_check_eq(data, rangeBody.substring(1));
 
     // Try a server which doesn't support range requests
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Range-Type", "none", false);
     chan.asyncOpen(new ChannelListener(try_no_range, null, CL_EXPECT_FAILURE), null);
@@ -123,7 +127,7 @@ function run_test() {
     do_check_eq(request.status, NS_ERROR_NOT_RESUMABLE);
 
     // Try a server which supports "bytes" range requests
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Range-Type", "bytes", false);
     chan.asyncOpen(new ChannelListener(try_bytes_range, null), null);
@@ -135,7 +139,7 @@ function run_test() {
     do_check_eq(data, rangeBody);
 
     // Try a server which supports "foo" and "bar" range requests
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Range-Type", "foo, bar", false);
     chan.asyncOpen(new ChannelListener(try_foo_bar_range, null, CL_EXPECT_FAILURE), null);
@@ -147,7 +151,7 @@ function run_test() {
     do_check_eq(request.status, NS_ERROR_NOT_RESUMABLE);
 
     // Try a server which supports "foobar" range requests
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Range-Type", "foobar", false);
     chan.asyncOpen(new ChannelListener(try_foobar_range, null, CL_EXPECT_FAILURE), null);
@@ -159,7 +163,7 @@ function run_test() {
     do_check_eq(request.status, NS_ERROR_NOT_RESUMABLE);
 
     // Try a server which supports "bytes" and "foobar" range requests
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Range-Type", "bytes, foobar", false);
     chan.asyncOpen(new ChannelListener(try_bytes_foobar_range, null), null);
@@ -171,7 +175,7 @@ function run_test() {
     do_check_eq(data, rangeBody);
 
     // Try a server which supports "bytesfoo" and "bar" range requests
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Range-Type", "bytesfoo, bar", false);
     chan.asyncOpen(new ChannelListener(try_bytesfoo_bar_range, null, CL_EXPECT_FAILURE), null);
@@ -183,7 +187,7 @@ function run_test() {
     do_check_eq(request.status, NS_ERROR_NOT_RESUMABLE);
 
     // Try a server which doesn't send Accept-Ranges header at all
-    var chan = make_channel("http://localhost:4444/acceptranges");
+    var chan = make_channel(URL + "/acceptranges");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.asyncOpen(new ChannelListener(try_no_accept_ranges, null), null);
   }
@@ -194,7 +198,7 @@ function run_test() {
     do_check_eq(data, rangeBody);
 
     // Try a successful suspend/resume from 0
-    var chan = make_channel("http://localhost:4444/range");
+    var chan = make_channel(URL + "/range");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.asyncOpen(new ChannelListener(try_suspend_resume, null,
                                        CL_SUSPEND | CL_EXPECT_3S_DELAY), null);
@@ -206,7 +210,7 @@ function run_test() {
     do_check_eq(data, rangeBody);
 
     // Try a successful resume from 0
-    var chan = make_channel("http://localhost:4444/range");
+    var chan = make_channel(URL + "/range");
     chan.nsIResumableChannel.resumeAt(0, entityID);
     chan.asyncOpen(new ChannelListener(success, null), null);
   }
@@ -219,7 +223,7 @@ function run_test() {
 
     // Authentication (no password; working resume)
     // (should not give us any data)
-    var chan = make_channel("http://localhost:4444/range");
+    var chan = make_channel(URL + "/range");
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Need-Auth", "true", false);
     chan.asyncOpen(new ChannelListener(test_auth_nopw, null, CL_EXPECT_FAILURE), null);
@@ -231,7 +235,8 @@ function run_test() {
     do_check_eq(request.status, NS_ERROR_ENTITY_CHANGED);
 
     // Authentication + not working resume
-    var chan = make_channel("http://guest:guest@localhost:4444/auth");
+    var chan = make_channel("http://guest:guest@localhost:" +
+                            httpserver.identity.primaryPort + "/auth");
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.notificationCallbacks = new Requestor();
     chan.asyncOpen(new ChannelListener(test_auth, null, CL_EXPECT_FAILURE), null);
@@ -242,7 +247,8 @@ function run_test() {
     do_check_true(request.nsIHttpChannel.responseStatus < 300);
 
     // Authentication + working resume
-    var chan = make_channel("http://guest:guest@localhost:4444/range");
+    var chan = make_channel("http://guest:guest@localhost:" +
+                            httpserver.identity.primaryPort + "/range");
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.notificationCallbacks = new Requestor();
     chan.nsIHttpChannel.setRequestHeader("X-Need-Auth", "true", false);
@@ -255,7 +261,7 @@ function run_test() {
     do_check_true(request.nsIHttpChannel.requestSucceeded);
 
     // 404 page (same content length as real content)
-    var chan = make_channel("http://localhost:4444/range");
+    var chan = make_channel(URL + "/range");
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.nsIHttpChannel.setRequestHeader("X-Want-404", "true", false);
     chan.asyncOpen(new ChannelListener(test_404, null, CL_EXPECT_FAILURE), null);
@@ -267,7 +273,7 @@ function run_test() {
     do_check_eq(request.nsIHttpChannel.responseStatus, 404);
 
     // 416 Requested Range Not Satisfiable
-    var chan = make_channel("http://localhost:4444/range");
+    var chan = make_channel(URL + "/range");
     chan.nsIResumableChannel.resumeAt(1000, entityID);
     chan.asyncOpen(new ChannelListener(test_416, null, CL_EXPECT_FAILURE), null);
   }
@@ -278,8 +284,8 @@ function run_test() {
     do_check_eq(request.nsIHttpChannel.responseStatus, 416);
 
     // Redirect + successful resume
-    var chan = make_channel("http://localhost:4444/redir");
-    chan.nsIHttpChannel.setRequestHeader("X-Redir-To", "http://localhost:4444/range", false);
+    var chan = make_channel(URL + "/redir");
+    chan.nsIHttpChannel.setRequestHeader("X-Redir-To", URL + "/range", false);
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.asyncOpen(new ChannelListener(test_redir_resume, null), null);
   }
@@ -291,8 +297,8 @@ function run_test() {
     do_check_eq(request.nsIHttpChannel.responseStatus, 206);
 
     // Redirect + failed resume
-    var chan = make_channel("http://localhost:4444/redir");
-    chan.nsIHttpChannel.setRequestHeader("X-Redir-To", "http://localhost:4444/", false);
+    var chan = make_channel(URL + "/redir");
+    chan.nsIHttpChannel.setRequestHeader("X-Redir-To", URL + "/", false);
     chan.nsIResumableChannel.resumeAt(1, entityID);
     chan.asyncOpen(new ChannelListener(test_redir_noresume, null, CL_EXPECT_FAILURE), null);
   }
@@ -304,8 +310,8 @@ function run_test() {
     httpserver.stop(do_test_finished);
   }
 
-  httpserver.start(4444);
-  var chan = make_channel("http://localhost:4444/range");
+  httpserver.start(-1);
+  var chan = make_channel(URL + "/range");
   chan.asyncOpen(new ChannelListener(get_entity_id, null), null);
   do_test_pending();
 }
diff --git a/netwerk/test/unit/test_resumable_truncate.js b/netwerk/test/unit/test_resumable_truncate.js
index a01beb973459..9ad81892bc63 100644
--- a/netwerk/test/unit/test_resumable_truncate.js
+++ b/netwerk/test/unit/test_resumable_truncate.js
@@ -71,21 +71,24 @@ function finish_test() {
 }
 
 function start_cache_read() {
-  var chan = make_channel("http://localhost:4444/cached/test.gz");
+  var chan = make_channel("http://localhost:" +
+                          httpserver.identity.primaryPort + "/cached/test.gz");
   chan.asyncOpen(new ChannelListener(finish_test, null), null);
 }
 
 function start_canceler() {
-  var chan = make_channel("http://localhost:4444/cached/test.gz");
+  var chan = make_channel("http://localhost:" +
+                          httpserver.identity.primaryPort + "/cached/test.gz");
   chan.asyncOpen(new Canceler(start_cache_read), null);
 }
 
 function run_test() {
   httpserver = new HttpServer();
   httpserver.registerPathHandler("/cached/test.gz", cachedHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
-  var chan = make_channel("http://localhost:4444/cached/test.gz");
+  var chan = make_channel("http://localhost:" +
+                          httpserver.identity.primaryPort + "/cached/test.gz");
   chan.asyncOpen(new ChannelListener(start_canceler, null), null);
   do_test_pending();
 }
diff --git a/netwerk/test/unit/test_simple.js b/netwerk/test/unit/test_simple.js
index 0b3546e66fd3..d07311b6b800 100644
--- a/netwerk/test/unit/test_simple.js
+++ b/netwerk/test/unit/test_simple.js
@@ -26,7 +26,7 @@ function run_test() {
 function setup_test() {
   if (dbg) { print("============== setup_test: in"); }
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
   var channel = setupChannel(testpath);
   // ChannelListener defined in head_channels.js
   channel.asyncOpen(new ChannelListener(checkRequest, channel), null);
@@ -36,7 +36,8 @@ function setup_test() {
 function setupChannel(path) {
   var ios = Cc["@mozilla.org/network/io-service;1"].
                        getService(Ci.nsIIOService);
-  var chan = ios.newChannel("http://localhost:4444" + path, "", null);
+  var chan = ios.newChannel("http://localhost:" +
+                            httpserver.identity.primaryPort + path, "", null);
   chan.QueryInterface(Ci.nsIHttpChannel);
   chan.requestMethod = "GET";
   return chan;
diff --git a/netwerk/test/unit/test_speculative_connect.js b/netwerk/test/unit/test_speculative_connect.js
index 364333fa7190..18563d8f94ae 100644
--- a/netwerk/test/unit/test_speculative_connect.js
+++ b/netwerk/test/unit/test_speculative_connect.js
@@ -9,7 +9,7 @@ const ServerSocket = CC("@mozilla.org/network/server-socket;1",
 var serv;
 
 function TestServer() {
-    this.listener = ServerSocket(4444, true, -1);
+    this.listener = ServerSocket(-1, true, -1);
     this.listener.asyncListen(this);
 }
 
@@ -34,7 +34,7 @@ function run_test() {
         .getService(Ci.nsIIOService);    
 
     serv = new TestServer();
-    URI = ios.newURI("http://localhost:4444/just/a/test", null, null);
+    URI = ios.newURI("http://localhost:" + serv.listener.port + "/just/a/test", null, null);
     ios.QueryInterface(Components.interfaces.nsISpeculativeConnect)
         .speculativeConnect(URI, null);
     do_test_pending();
diff --git a/netwerk/test/unit/test_traceable_channel.js b/netwerk/test/unit/test_traceable_channel.js
index d73157b76183..954f6db5ad23 100644
--- a/netwerk/test/unit/test_traceable_channel.js
+++ b/netwerk/test/unit/test_traceable_channel.js
@@ -10,7 +10,10 @@ const Cr = Components.results;
 
 Cu.import("resource://testing-common/httpd.js");
 
-var httpserver = null;
+var httpserver = new HttpServer();
+httpserver.start(-1);
+const PORT = httpserver.identity.primaryPort;
+
 var pipe = null;
 var streamSink = null;
 
@@ -31,9 +34,9 @@ TracingListener.prototype = {
 /*
     do_check_eq(request.localAddress, "127.0.0.1");
     do_check_eq(request.localPort > 0, true);
-    do_check_neq(request.localPort, 4444);
+    do_check_neq(request.localPort, PORT);
     do_check_eq(request.remoteAddress, "127.0.0.1");
-    do_check_eq(request.remotePort, 4444);
+    do_check_eq(request.remotePort, PORT);
 */
 
     // Make sure listener can't be replaced after OnStartRequest was called.
@@ -147,11 +150,9 @@ function run_test() {
   var observer = new HttpResponseExaminer();
   observer.register();
 
-  httpserver = new HttpServer();
   httpserver.registerPathHandler("/testdir", test_handler);
-  httpserver.start(4444);
 
-  var channel = make_channel("http://localhost:4444/testdir");
+  var channel = make_channel("http://localhost:" + PORT + "/testdir");
   channel.asyncOpen(new ChannelListener(channel_finished), null);
   do_test_pending();
 }
diff --git a/netwerk/test/unit/test_xmlhttprequest.js b/netwerk/test/unit/test_xmlhttprequest.js
index 505892d8bd9b..b951fc55c1c2 100644
--- a/netwerk/test/unit/test_xmlhttprequest.js
+++ b/netwerk/test/unit/test_xmlhttprequest.js
@@ -13,7 +13,8 @@ function createXHR(async)
 {
   var xhr = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"]
             .createInstance(Ci.nsIXMLHttpRequest);
-  xhr.open("GET", "http://localhost:4444" + testpath, async);
+  xhr.open("GET", "http://localhost:" +
+           httpserver.identity.primaryPort + testpath, async);
   return xhr;
 }
 
@@ -33,7 +34,7 @@ function checkResults(xhr)
 function run_test()
 {
   httpserver.registerPathHandler(testpath, serverHandler);
-  httpserver.start(4444);
+  httpserver.start(-1);
 
   // Test sync XHR sending
   var sync = createXHR(false);
diff --git a/netwerk/test/unit/xpcshell.ini b/netwerk/test/unit/xpcshell.ini
index cb2bad2eee19..9a0ae2a0a9fb 100644
--- a/netwerk/test/unit/xpcshell.ini
+++ b/netwerk/test/unit/xpcshell.ini
@@ -185,7 +185,9 @@ run-if = hasNode
 [test_XHR_redirects.js]
 [test_pinned_app_cache.js]
 [test_offlinecache_custom-directory.js]
+run-sequentially = Hardcoded hash value includes port 4444.
 [test_bug767025.js]
+run-sequentially = Hardcoded hash value includes port 4444.
 [test_bug826063.js]
 [test_bug812167.js]
 [test_tldservice_nextsubdomain.js]
diff --git a/netwerk/test/unit_ipc/head_channels_clone.js b/netwerk/test/unit_ipc/head_channels_clone.js
index b947d093ef70..f5eb45cbb8b1 100644
--- a/netwerk/test/unit_ipc/head_channels_clone.js
+++ b/netwerk/test/unit_ipc/head_channels_clone.js
@@ -2,5 +2,7 @@
 // Load standard base class for network tests into child process
 //
 
+Components.utils.import('resource://gre/modules/XPCOMUtils.jsm');
+
 load("../unit/head_channels.js");