add 'drain' emit to WS

lib/transports/websocket.js

@@ -82,9 +82,17 @@ WS.prototype.doOpen = function(){
  */
 
 WS.prototype.write = function(packets){
-  for (var i = 0, l = packets.length; i < l; i++) {
-    this.socket.send(parser.encodePacket(packets[i]));
-  }
+  // encodePayload instead of encodePacket
+  this.writable = false;
+  this.socket.send(parser.encodePayload(packets));
+  // check periodically if we're done sending
+  var bufferedAmountId = this.setInterval(function() {
+    if (socket.bufferedAmount == 0) {
+      clearInterval(bufferedAmountId);
+      this.writable = true;
+      this.emit('drain');
+    }
+  }, 50);
 };
 
 /**