Issue with WebSocket Connection Not Forwarding Messages to Client

[barisgundem]

Problem Description:
I'm experiencing an issue with WebSocket communication in a project where both the backend and frontend are running in Docker containers. When I send a POST request to localhost:5173/api/notify, it returns a 200 status, but the message is not being forwarded to the client as expected.

Setup Overview:

The frontend is built using React and Vite, with WebSocket communication implemented using socket.io-client.
The backend handles WebSocket connections and is proxied through Vite's development server.
WebSocket communication is established by emitting a 'register' event from the client and listening for 'forwardedMessage' events.

Code Snippets:

WebSocket Initialization (useWS.tsx):

import { useEffect } from 'react';
import { useDispatch, useSelector } from 'react-redux';
import { io } from "socket.io-client";

export const useWS = () => {
  const dispatch = useDispatch();
  const user = useSelector((state: RootState) => state.auth.user);
  let socket: any = null;
  let link = "";

  useEffect(() => {
    if (user) {
      link = import.meta.env.VITE_SERVICES_ORCH_URL || "/websocket";
      socket = io(link);

      // Register the user with a userId
      socket.emit('register', user.user_id);

      // Listen for forwarded messages
      socket.on('forwardedMessage', (data: any) => {
        console.log('Received forwarded message:', data);
      });
    }

    // Cleanup on component unmount
    return () => {
      if (socket) {
        socket.disconnect();
      }
    };
  }, [user]);
};

Vite Configuration (vite.config.ts):

export default defineConfig(({ command, mode }) => {
  return {
    server: {
      proxy: {
        '/api/notify': {
          target: 'http://servicesorch:3000/notify/forward',
          changeOrigin: true,
          rewrite: (path) => path.replace(/^\/api\/notify/, ''),
        },
        '/websocket': {
          target: 'ws://servicesorch:3000',
          ws: true,
          changeOrigin: true,
        },
      },
    },
  };
});

Issue Details:

Despite the WebSocket connection being successfully established and the POST request to localhost:5173/api/notify returning a 200 status, the client does not receive any forwarded messages.
The logs confirm that the WebSocket connection is made and the 'register' event is emitted, but no 'forwardedMessage' events are captured.
Questions:

Is there anything I might be missing in the Vite configuration or the WebSocket setup that could prevent messages from being forwarded to the client?
Could the issue be related to the way Docker handles networking between containers?
Any suggestions for debugging this issue further?

Environment:

Vite version: vite/5.4.0 darwin-arm64 node-v20.16.0
React version: ^18.3.1
socket.io-client version: ^4.7.5
Docker environment: Docker version 27.0.3, build 7d4bcd8
Running both frontend and backend in Docker containers

Any help or insights would be greatly appreciated!