[fix minor] Prevent crashes from attempting to remove listeners more than once when proxying websocket requests.

Author: indexzero

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

@@ -472,6 +472,8 @@ HttpProxy.prototype.proxyWebSocketRequest = function (req, socket, head, buffer)
   // the appropriate events.
   //
   function onUpgrade (reverseProxy, proxySocket) {
+    var detached;
+
     if (!reverseProxy) {
       proxySocket.end();
       socket.end();
@@ -543,12 +545,15 @@ HttpProxy.prototype.proxyWebSocketRequest = function (req, socket, head, buffer)
     // from `reverseProxy` and `proxySocket`.
     //
     function detach() {
-      proxySocket.destroySoon();
-      proxySocket.removeListener('end', listeners.onIncomingClose);
-      proxySocket.removeListener('data', listeners.onIncoming);
-      reverseProxy.incoming.socket.destroySoon();
-      reverseProxy.incoming.socket.removeListener('end', listeners.onOutgoingClose);
-      reverseProxy.incoming.socket.removeListener('data', listeners.onOutgoing);
+      if (!detached) {
+        detached = true;
+        proxySocket.destroySoon();
+        proxySocket.removeListener('end', listeners.onIncomingClose);
+        proxySocket.removeListener('data', listeners.onIncoming);
+        reverseProxy.incoming.socket.destroySoon();
+        reverseProxy.incoming.socket.removeListener('end', listeners.onOutgoingClose);
+        reverseProxy.incoming.socket.removeListener('data', listeners.onOutgoing);
+      }
     }
 
    //