[feature] add localAddress option (#487)

Author: magicdawn

README.md

@@ -226,6 +226,7 @@ Exposed as `eio` in the browser standalone build.
       - `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)
+      - `localAddress` (`String`): the local IP address to connect to
 - `send`
     - Sends a message to the server
     - **Parameters**

lib/socket.js

@@ -100,6 +100,10 @@ function Socket (uri, opts) {
     if (opts.extraHeaders && Object.keys(opts.extraHeaders).length > 0) {
       this.extraHeaders = opts.extraHeaders;
     }
+
+    if (opts.localAddress) {
+      this.localAddress = opts.localAddress;
+    }
   }
 
   // set on handshake
@@ -186,7 +190,8 @@ Socket.prototype.createTransport = function (name) {
     rejectUnauthorized: this.rejectUnauthorized,
     perMessageDeflate: this.perMessageDeflate,
     extraHeaders: this.extraHeaders,
-    forceNode: this.forceNode
+    forceNode: this.forceNode,
+    localAddress: this.localAddress
   });
 
   return transport;

lib/transport.js

@@ -43,6 +43,7 @@ function Transport (opts) {
 
   // other options for Node.js client
   this.extraHeaders = opts.extraHeaders;
+  this.localAddress = opts.localAddress;
 }
 
 /**

lib/transports/websocket.js

@@ -103,6 +103,9 @@ WS.prototype.doOpen = function () {
   if (this.extraHeaders) {
     opts.headers = this.extraHeaders;
   }
+  if (this.localAddress) {
+    opts.localAddress = this.localAddress;
+  }
 
   try {
     this.ws = this.usingBrowserWebSocket ? new WebSocket(uri) : new WebSocket(uri, protocols, opts);