How to spin up a websocket server paralelly along with express app?

Question

I have an express application, and a websocket script. I create the server and spinup the express app in a www.js file.

The problem I'm facing is that, I'm not able to instantiate the websocket inside the www.js file.

Here is the www.js

....
const server = http.createServer(app);
server.listen(port);
server.on("error", onError);
server.on("listening", onListening);
....

Here is the websocket.js

const WebSocket = require('ws');

const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });

  ws.send('something');
});

I know the line const wss = new Websocket.Server({ port: 8080 }); creates the websocket instance...but I want to be able to create this instance in www.js file and all the logic for websocket in a seperate file.

Answer 1

Pass the http server instance to the websocket server,

const wss = new Websocket.Server({ server: server });

---

If you want to separate it as a single modules to a file,

const WebSocket = require('ws');


const initWSServer = (server) => {
  const wss = new WebSocket.Server({ server: server});

  wss.on('connection', function connection(ws) {

    ws.on('message', function incoming(message) {
      console.log('received: %s', message);
    });

    ws.send('something');

  });
}

module.exports = {
  initWSServer
}

Then,

const server = http.createServer(app);
server.listen(port);
server.on("error", onError);
server.on("listening", onListening);

const ws_server = require('./websocket.js');
ws_server.initWSServer(server);