Fix for http-party#458. Host header may cause some sites not to be proxyable with changeOrigin enabled

Author: janjongboom

Diff for: lib/node-http-proxy/http-proxy.js

@@ -237,7 +237,14 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
   // don't revert this without documenting it!
   //
   if (this.changeOrigin) {
-    outgoing.headers.host = this.target.host + ':' + this.target.port;
+    outgoing.headers.host = this.target.host;
+    // Only add port information to the header if not default port
+    // for this protocol. 
+    // See https://github.com/nodejitsu/node-http-proxy/issues/458
+    if (this.target.port !== 443 && this.target.https ||
+        this.target.port !== 80 && !this.target.https) {
+      outgoing.headers.host += ':' + this.target.port;
+    }
   }
 
   //