fixed ws issue 1256

lib/server.js

@@ -55,6 +55,10 @@ app._initializeWSS = function(server) {
       self._configureWS(socket, key, id, token);
     }
   });
+
+  this._wss.on("error", function (err) {
+    // handle error
+  })
 };
 
 app._configureWS = function(socket, key, id, token) {