[fix] x-forwarded http headers should set properly.

lib/node-http-proxy/http-proxy.js

@@ -128,9 +128,10 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
   // * `x-forwarded-proto`: Protocol of the original request
   // * `x-forwarded-port`: Port of the original request.
   //
-  if (this.enable.xforward && req.connection && req.connection.socket) {
+
+  if (this.enable.xforward && req.connection && req.socket) {
     req.headers['x-forwarded-for']   = req.connection.remoteAddress || req.connection.socket.remoteAddress;
-    req.headers['x-forwarded-port']  = req.connection.remotePort || req.connection.socket.remotePort;
+    req.headers['x-forwarded-port']  = req.connection.remotePort || req.socket.remotePort;
     req.headers['x-forwarded-proto'] = req.connection.pair ? 'https' : 'http';
   }
 
@@ -763,4 +764,4 @@ HttpProxy.prototype._forwardRequest = function (req) {
   req.on('end', function () {
     forwardProxy.end();
   });
-};
\ No newline at end of file
+};