[feature] Added flag forceNode to override the normal behavior of prefering Browser based implementations. (#469)

Author: Eusebius1920

README.md

@@ -225,6 +225,7 @@ Exposed as `eio` in the browser standalone build.
       - `extraHeaders` (`Object`): Headers that will be passed for each request to the server (via xhr-polling and via websockets). These values then can be used during handshake or for special proxies. Can only be used in Node.js client environment.
       - `onlyBinaryUpgrades` (`Boolean`): whether transport upgrades should be restricted to transports supporting binary data (`false`)
       - `requestTimeout` (`Number`): Timeout for xhr-polling requests in milliseconds (`0`)
+      - `forceNode` (`Boolean`): Uses NodeJS implementation for websockets - even if there is a native Browser-Websocket available, which is preferred by default over the NodeJS implementation. (This is useful when using hybrid platforms like nw.js or electron) (`false`, NodeJS only)
 - `send`
     - Sends a message to the server
     - **Parameters**

lib/socket.js

@@ -92,6 +92,7 @@ function Socket (uri, opts) {
   this.ca = opts.ca || null;
   this.ciphers = opts.ciphers || null;
   this.rejectUnauthorized = opts.rejectUnauthorized === undefined ? null : opts.rejectUnauthorized;
+  this.forceNode = !!opts.forceNode;
 
   // other options for Node.js client
   var freeGlobal = typeof global === 'object' && global;
@@ -184,7 +185,8 @@ Socket.prototype.createTransport = function (name) {
     ciphers: this.ciphers,
     rejectUnauthorized: this.rejectUnauthorized,
     perMessageDeflate: this.perMessageDeflate,
-    extraHeaders: this.extraHeaders
+    extraHeaders: this.extraHeaders,
+    forceNode: this.forceNode
   });
 
   return transport;

lib/transport.js

@@ -39,6 +39,7 @@ function Transport (opts) {
   this.ca = opts.ca;
   this.ciphers = opts.ciphers;
   this.rejectUnauthorized = opts.rejectUnauthorized;
+  this.forceNode = opts.forceNode;
 
   // other options for Node.js client
   this.extraHeaders = opts.extraHeaders;

lib/transports/websocket.js

@@ -9,6 +9,12 @@ var inherit = require('component-inherit');
 var yeast = require('yeast');
 var debug = require('debug')('engine.io-client:websocket');
 var BrowserWebSocket = global.WebSocket || global.MozWebSocket;
+var NodeWebSocket;
+if (typeof window === 'undefined') {
+  try {
+    NodeWebSocket = require('ws');
+  } catch (e) { }
+}
 
 /**
  * Get either the `WebSocket` or `MozWebSocket` globals
@@ -18,9 +24,7 @@ var BrowserWebSocket = global.WebSocket || global.MozWebSocket;
 
 var WebSocket = BrowserWebSocket;
 if (!WebSocket && typeof window === 'undefined') {
-  try {
-    WebSocket = require('ws');
-  } catch (e) { }
+  WebSocket = NodeWebSocket;
 }
 
 /**
@@ -42,6 +46,10 @@ function WS (opts) {
     this.supportsBinary = false;
   }
   this.perMessageDeflate = opts.perMessageDeflate;
+  this.usingBrowserWebSocket = BrowserWebSocket && !opts.forceNode;
+  if (!this.usingBrowserWebSocket) {
+    WebSocket = NodeWebSocket;
+  }
   Transport.call(this, opts);
 }
 
@@ -97,7 +105,7 @@ WS.prototype.doOpen = function () {
   }
 
   try {
-    this.ws = BrowserWebSocket ? new WebSocket(uri) : new WebSocket(uri, protocols, opts);
+    this.ws = this.usingBrowserWebSocket ? new WebSocket(uri) : new WebSocket(uri, protocols, opts);
   } catch (err) {
     return this.emit('error', err);
   }
@@ -156,7 +164,7 @@ WS.prototype.write = function (packets) {
   for (var i = 0, l = total; i < l; i++) {
     (function (packet) {
       parser.encodePacket(packet, self.supportsBinary, function (data) {
-        if (!BrowserWebSocket) {
+        if (!self.usingBrowserWebSocket) {
           // always create a new object (GH-437)
           var opts = {};
           if (packet.options) {
@@ -175,7 +183,7 @@ WS.prototype.write = function (packets) {
         // have a chance of informing us about it yet, in that case send will
         // throw an error
         try {
-          if (BrowserWebSocket) {
+          if (self.usingBrowserWebSocket) {
             // TypeError is thrown when passing the second argument on Safari
             self.ws.send(data);
           } else {