diff --git a/node_modules/c9/urls.js b/node_modules/c9/urls.js
index b446ff31..c48a3cff 100644
--- a/node_modules/c9/urls.js
+++ b/node_modules/c9/urls.js
@@ -9,16 +9,35 @@
 var assert = require("assert");
 
 function getHost(req) {
-    if (req.headers)
-        return req.headers.host;
+    var host = 
+        req.headers && req.headers.host ||
+        req.host ||
+        req.url ||
+        req;
+        
+    return host.replace(/^https?:\/\/([^/]*).*/, "$1");
+}
 
-    if (req.host)
-        return req.host;
+function splitDomain(req, domains) {
+    var host = getHost(req);
+    
+    var allDomains = domains.join("|");
+    var domainRe = new RegExp("^(.*?)\\.?(" + allDomains.replace(".", "\\.") + ")(?::(\\d+))?$");
 
-    if (req.url)
-        return req.url.replace(/^https?:\/\/([^/]*).*/, "$1");
-
-    return req;
+    var m = host.match(domainRe);
+    if (m) {
+        return {
+            subDomains: m[1],
+            domainName: m[2],
+            port: m[3] || ""
+        };
+    } else {
+        return {
+            subDomains: "",
+            domainName: host.split(":")[0],
+            port: host.split(":")[1] || ""
+        };
+    }
 }
 
 /**
@@ -115,4 +134,6 @@ function replaceDomain(url, domain) {
 module.exports = {
     replaceDomains: replaceDomains,
     getBaseUrl: getBaseUrl,
+    splitDomain: splitDomain,
+    getHost: getHost
 };
\ No newline at end of file
diff --git a/node_modules/c9/urls_test.js b/node_modules/c9/urls_test.js
index 9e5bc0ec..18cd3fe6 100644
--- a/node_modules/c9/urls_test.js
+++ b/node_modules/c9/urls_test.js
@@ -9,7 +9,7 @@ if (typeof define === "undefined") {
     require("../../test/setup_paths");
 }
 
-var assert = require("assert");
+var assert = require("assert-diff");
 var urls = require("./urls");
 var url = require("url");
 var sinon = require("sinon");
@@ -126,4 +126,28 @@ describe("urls", function() {
         var baseUrl = urls.getBaseUrl(input, "https://preview.$DOMAIN");
         assert.equal(baseUrl, "https://preview.newclient-lennartcl.c9.io");
     });
+    
+    it("should split domains", function() {
+        var domains = ["c9.io", "c9users.io", "cs50.io"];
+        assert.deepEqual(urls.splitDomain("fjakobs-ace.c9.io", domains), {
+            domainName: "c9.io",
+            subDomains: "fjakobs-ace",
+            port: ""
+        });
+        assert.deepEqual(urls.splitDomain("preview.c9users.io", domains), {
+            domainName: "c9users.io",
+            subDomains: "preview",
+            port: ""
+        });
+        assert.deepEqual(urls.splitDomain("fjakobs.ace.cs50.io", domains), {
+            domainName: "cs50.io",
+            subDomains: "fjakobs.ace",
+            port: ""
+        });
+        assert.deepEqual(urls.splitDomain("fjakobs.ace.cs50.io:8081", domains), {
+            domainName: "cs50.io",
+            subDomains: "fjakobs.ace",
+            port: "8081"
+        });
+    });
 });
\ No newline at end of file