add support for drain event and send response boolean to make sockjs compliant with Writeable api that allows for handling back pressure

Author: avistramer

lib/main.js

@@ -164,7 +164,7 @@ SockJS.prototype.send = function(data) {
   if (this.readyState !== SockJS.OPEN) {
     return;
   }
-  this._transport.send(escape.quote(data));
+  return this._transport.send(escape.quote(data));
 };
 
 SockJS.version = require('./version');
@@ -223,6 +223,10 @@ SockJS.prototype._connect = function() {
     debug('transport url', transportUrl);
     var transportObj = new Transport(transportUrl, this._transUrl, options);
     transportObj.on('message', this._transportMessage.bind(this));
+    // for transports that support backpressure handle drain event
+    transportObj.on('drain', function() {
+      self.dispatchEvent(new Event('drain'));
+    });
     transportObj.once('close', this._transportClose.bind(this));
     transportObj.transportName = Transport.transportName;
     this._transport = transportObj;

lib/transport/iframe.js

@@ -128,6 +128,7 @@ IframeTransport.prototype.postMessage = function(type, data) {
 IframeTransport.prototype.send = function(message) {
   debug('send', message);
   this.postMessage('m', message);
+  return true;
 };
 
 IframeTransport.enabled = function() {

lib/transport/lib/buffered-sender.js

@@ -25,6 +25,7 @@ BufferedSender.prototype.send = function(message) {
   if (!this.sendStop) {
     this.sendSchedule();
   }
+  return true;
 };
 
 // For polling transports in a situation when in the message callback,

lib/transport/websocket.js

@@ -54,14 +54,17 @@ function WebSocketTransport(transUrl, ignore, options) {
     self.emit('close', 1006, 'WebSocket connection broken');
     self._cleanup();
   };
+  this.ws.on('drain', function() {
+    self.emit('drain');
+  })
 }
 
 inherits(WebSocketTransport, EventEmitter);
 
 WebSocketTransport.prototype.send = function(data) {
   var msg = '[' + data + ']';
   debug('send', msg);
-  this.ws.send(msg);
+  return this.ws.send(msg);
 };
 
 WebSocketTransport.prototype.close = function() {