Add method were we can emit and listen to server

[elmcapp]

I am using socket.io with express to create a tunnel server something like localtunnel.me I am in the need to be able to emit messages from the server and be able to listen to the emitted data in the same server. I was thinking of using io.addListener but it does not do anything.

Goal:
The server can for example io.addListener or. io.on("in_server", console.log)
The server can io.emit("in_server", "data here")
when the emit happen in the server the server can also listen.

By doing something like this I would be able to use the data outside the:

io.on("connection", (socket) => {})

[vitaly-t]

What is the point of using sockets for communicating data inside one process? 😕

[Shekharcodess]

To achieve your goal of emitting messages from the server and being able to listen to those emitted messages within the same server using Socket.IO and Express. You have to set up the Socket.IO server within your Express server

[elmcapp]

To achieve your goal of emitting messages from the server and being able to listen to those emitted messages within the same server using Socket.IO and Express. You have to set up the Socket.IO server within your Express server

Can you show an example below is some what that I am trying to do however I know it's not right. I am new to this.

import EventEmitter from "events";
import express from "express";
import http from "http";
import { Server } from "socket.io";

const app = express();
const emitter = new EventEmitter();

// socket
const server = http.createServer(app);
const io = new Server(server, {
  cors: {
    origin: "*",
  },
});

app.set(express.urlencoded({ extended: false }));

app.set(express.json());

// browser page
app.get("/", (req, res) => {
  const url = req.url;

  // emit to the remote host
  io.to(socketId).emit("host", url);

  // Send response back to client
  emitter.addListener("response", (data) => {
    res.send(data);
  });
});

// socket connection
io.on("connection", (socket) => {
  //Listen to to remote host 
  socket.on("remote_response", (data) => {
    emitter.emit("response", data);
  });
});

server.listen(9800, () => {
  console.log("server is running");
});

[Shekharcodess]

To achieve your goal of emitting messages from the server and being able to listen to those emitted messages within the same server using Socket.IO and Express. You have to set up the Socket.IO server within your Express server

Can you show an example below is some what that I am trying to do however I know it's not right. I am new to this.

import EventEmitter from "events";
import express from "express";
import http from "http";
import { Server } from "socket.io";

const app = express();
const emitter = new EventEmitter();

// socket
const server = http.createServer(app);
const io = new Server(server, {
  cors: {
    origin: "*",
  },
});

app.set(express.urlencoded({ extended: false }));

app.set(express.json());

// browser page
app.get("/", (req, res) => {
  const url = req.url;

  // emit to the remote host
  io.to(socketId).emit("host", url);

  // Send response back to client
  emitter.addListener("response", (data) => {
    res.send(data);
  });
});

// socket connection
io.on("connection", (socket) => {
  //Listen to to remote host 
  socket.on("remote_response", (data) => {
    emitter.emit("response", data);
  });
});

server.listen(9800, () => {
  console.log("server is running");
});

You can try adding these modifications to your code.

import EventEmitter from "events";
import express from "express";
import http from "http";
import { Server } from "socket.io";

const app = express();
const emitter = new EventEmitter();

// socket
const server = http.createServer(app);
const io = new Server(server, {
cors: {
origin: "*",
},
});

app.set(express.urlencoded({ extended: false }));
app.set(express.json());

// Listen to "in_server" event on the server
io.on("in_server", (data) => {
console.log("Received 'in_server' event:", data);
});

// browser page
app.get("/", (req, res) => {
const url = req.url;

// Emit "in_server" event from the server
io.emit("in_server", "data here");

// Send response back to client
emitter.addListener("response", (data) => {
res.send(data);
});
});

// socket connection
io.on("connection", (socket) => {
// Listen to "remote_response" event from remote host
socket.on("remote_response", (data) => {
emitter.emit("response", data);
});
});

server.listen(9800, () => {
console.log("server is running");
});

[elmcapp]

@Shekharcodess I try code similar to your example however io.on for the in_server never fire

// Listen to "in_server" event on the server
io.on("in_server", (data) => {
  console.log("Received 'in_server' event:", data);
});

app.get("/", (req, res) => {
  // Emit "in_server" event from the server
  io.emit("in_server", "data here");

  // Send placehold data back to browser for now
  res.send("placeholder data");
});

[elmcapp]

I found a solution that will allow to emit and listen to the emits from anywhere regardless of being in io.on("connection" ,socket) callback.

I am able to emit and listen to server emits using

// Listen to "in_server" event on the server
io.engine.on("in_server", (data) => {
  console.log("Received 'in_server' event:", data);
});

io.engine.emit("in_server", "hey there");

Although I am not sure what io.engine do

[Shekharcodess]

@elmcapp basically in Socket.IO, io.engine property provides access to the underlying Engine.IO instance. Engine.IO is the low-level transport layer that powers Socket.IO and handles the real-time communication between the server and the client.
Can you check if it supports emitting or listening to custom events? Because I think io.engine does not support that

[elmcapp]

Yes it's working with custom events. I created an event called in_server and another event called server-event and its working

[darrachequesne]

I think this can be closed now. Please reopen if needed.