Add support for web socket middle wares

lib/node-http-proxy.js

@@ -177,6 +177,16 @@ exports.createServer = function () {
     ? https.createServer(options.https, handler)
     : http.createServer(handler);
 
+  //
+  // process websocket as well if middleware(s) use(s) it
+  //
+  websocketHandler = exports.stackWebSocket(handlers, proxy);
+  if (websocketHandler != undefined) {
+    server.on('upgrade', function (req, socket, head) {
+      websocketHandler(req, socket, head);
+    });
+  }
+
   server.on('close', function () {
     proxy.close();
   });
@@ -326,6 +336,53 @@ exports.stack = function stack (middlewares, proxy) {
   return handle;
 };
 
+//
+// ### function stackWebSocket (middlewares, proxy)
+// #### @middlewares {Array} Array of functions to stack.
+// #### @proxy {HttpProxy|RoutingProxy} Proxy instance to 
+// Iteratively build up a single handler to the `http.Server`
+// `request` event (i.e. `function (req, res)`) by wrapping
+// each middleware `layer` into a `child` middleware which 
+// is in invoked by the parent (i.e. predecessor in the Array).
+//
+// adapted from https://github.com/creationix/stack
+//
+exports.stackWebSocket = function stackWebSocket (middlewares, proxy) {
+  var handle;
+  middlewares.reverse().forEach(function (layer) {
+    //
+    // Check if middleware as websocket strategy. If so, add it
+    //
+    if (!layer.proxyWebSocketRequest) return;
+    var child = handle;
+    handle = function (req, socket, head) {
+      var next = function (err) {
+        if (err) {
+          socket.end();
+          console.error('Error in websocket middleware(s): %s', err.stack);
+          return;
+        }
+        
+        if (child) {
+          child(req, res);
+        }
+      };
+
+      //
+      // Set the prototype of the `next` function to the instance
+      // of the `proxy` so that in can be used interchangably from
+      // a `connect` style callback and a true `HttpProxy` object.
+      //
+      // e.g. `function (req, res, next)` vs. `function (req, res, proxy)`
+      //
+      next.__proto__ = proxy;
+      layer.proxyWebSocketRequest(req, socket, head, next);
+    };
+  });
+
+  return handle;
+};
+
 //
 // ### function _getAgent (host, port, secure)
 // #### @options {Object} Options to use when creating the agent.