feat: ability to subscribe on websocket client/server senders

README.md

@@ -435,8 +435,6 @@ If you are using the `proxyServer.listen` method, the following options are also
 * `proxyReq`: This event is emitted before the data is sent. It gives you a chance to alter the proxyReq request object. Applies to "web" connections
 * `proxyReqWs`: This event is emitted before the data is sent. It gives you a chance to alter the proxyReq request object. Applies to "websocket" connections
 * `proxyRes`: This event is emitted if the request to the target got a response.
-* `wsClientMsg`: This event is emitted after webscoket mesage is sended from the client to the server.
-* `wsServerMsg`: This event is emitted after websocket message is sended from the server to the client.
 * `open`: This event is emitted once the proxy websocket was created and piped into the target websocket.
 * `close`: This event is emitted once the proxy websocket was closed.
 * (DEPRECATED) `proxySocket`: Deprecated in favor of `open`.
@@ -489,6 +487,39 @@ proxy.on('close', function (res, socket, head) {
 
 **[Back to top](#table-of-contents)**
 
+### Listening for websocket proxy request events
+
+* `clientSenderInited`: This event is emitted after websocket sender from client to server is initialized.
+* `serverSenderInited`: This event is emitted after websocket sender from server to client is initialized.
+* `wsClientMsg`: This event is emitted after webscoket message is sended from the client to the server.
+* `wsServerMsg`: This event is emitted after websocket message is sended from the server to the client.
+
+```js
+httpProxy.createServer({
+  target: 'ws://localhost:9014',
+  ws: true
+}).listen(8014);
+
+proxyServer.on('upgrade', function (req, socket, head) {
+  proxy.ws(req, socket, head);
+});
+
+proxyServer.on('proxyReqWs', (proxyReq, req, socket, options, head) => {
+  proxyReq.on('clientSenderInited', (sender) => {
+    sender.send('hello from client');
+  });
+
+  proxyReq.on('serverSenderInited', (sender) => {
+    sender.send('hello from server');
+  });
+
+  proxyReq.on('wsClientMsg', console.log);
+  proxyReq.on('wsServerMsg', console.log);
+});
+```
+
+**[Back to top](#table-of-contents)**
+
 ### Shutdown
 
 * When testing or running server within another program it may be necessary to close the proxy.

lib/http-proxy/ws/interceptor.js

@@ -77,6 +77,7 @@ module.exports = class Interceptor {
     _interceptClientMessages() {
         const receiver = new Receiver(this._clientExtensions);
         const sender = new Sender(this._proxySocket, this._serverExtensions);
+        this._proxyReq.emit('clientSenderInited', sender);
 
         // frame must be masked when send from client to server - https://tools.ietf.org/html/rfc6455#section-5.3
         const options = {mask: true};
@@ -92,6 +93,7 @@ module.exports = class Interceptor {
     _interceptServerMessages() {
         const receiver = new Receiver(this._serverExtensions);
         const sender = new Sender(this._socket, this._clientExtensions);
+        this._proxyReq.emit('serverSenderInited', sender);
 
         const options = {mask: false};
         const dataSender = this._getDataSender({sender, event: 'wsServerMsg', options});