Sending messages from one Socket.io server to another specific server

Question

Sending messages from one Socket.io server to another specific server

I am facing a unique scenario where a client (browser) connects to server A, which in turn is connected to server B and C. When the client sends a message to server A, I need to route that message to a specific server, either B or C, but not both. Essentially, I require isolated communication between servers rather than broadcasting the message to all connected servers.

How can I directly send messages to a single server? Below is my code snippet for setting up connections with the servers by adjusting the port numbers accordingly:

// Loading required modules
var PORT = process.env.PORT || 8080; // Change port based on server
var express = require("express");
var app = express();
var http = require("http").Server(app);
var io = require("socket.io")(http);

app.use(express.static(__dirname + '/public'));

var client = require('socket.io-client');

var socket1 = client.connect('http://localhost:8081', { reconnect: true }); // Connect to server B
var socket2 = client.connect('http://localhost:8082', { reconnect: true }); // Connect to server C

// Establishing connection listener
io.on('connection', function (socket) {
    console.log('Client connected.');
    
    // Listening for message from client
    socket.on('message_from_browser', function (message) {
        console.log("Browser message broadcasted: " + message.text);
        var updated_message = {
           text: message.text,
           port: PORT  
        };

        // Send message to server B
        socket1.emit('server_message', updated_message); 
    });

    // Disconnection listener
    socket.on('disconnect', function () {
        console.log('Client disconnected.');
    });
});

socket1.on('connect', function () {
    socket1.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM SERVER ON PORT '+ message.port + ": " + message.text);
    });
    console.log('Connected to server B!');
});

socket2.on('connect', function () {
    socket2.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM SERVER ON PORT '+ message.port + ": " + message.text);
    });
    console.log('Connected to server C!');
});

http.listen(PORT, function (req, res) {
    console.log("Server Started on port: " + PORT);
});

node.js express socket.io

Answer 1

Answer №1

A conflict arises with the variable name socket. It is used to define both the connection to server B and as an argument in your

.on('connection', function(socket) {...})

callback.

To resolve this, make the following changes:

var socket1 = client.connect('http://localhost:8081', { reconnect: true });//connection to server B
var socket2 = client.connect('http://localhost:8082', { reconnect: true });//connection to server C

Now, refer to the connection to server B as socket1, instead of socket.

The variable named socket is already being used as an argument here, causing a conflict:

// Add a connect listener
io.on('connection', function (socket) {
    console.log('Client connected.');

    //when server receives message from client
    socket.on('message_from_browser', function (message) {
        console.log("Message from browser broadcasted: " + message.text);
        
        var updated_message = {
           text: message.text,
           port: PORT  
        };

        // send message to server B
        socket1.emit('server_message', updated_message);//send message to server B
    });

    // Disconnect listener
    socket.on('disconnect', function () {
        console.log('Client disconnected.');
    });
});

You also need to add listeners for incoming server messages for both socket1 and socket2.

io.on('connect', function(socket1){
    socket1.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM ANOTHER SERVER ON PORT '+ message.port + ": " + message.text);
    });
});

io.on('connect', function(socket2){
    socket2.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM ANOTHER SERVER ON PORT '+ message.port + ": " + message.text);
    });
});

Answer 2

A conflict arises with the variable name socket. It is used to define both the connection to server B and as an argument in your

.on('connection', function(socket) {...})

callback.

To resolve this, make the following changes:

var socket1 = client.connect('http://localhost:8081', { reconnect: true });//connection to server B
var socket2 = client.connect('http://localhost:8082', { reconnect: true });//connection to server C

Now, refer to the connection to server B as socket1, instead of socket.

The variable named socket is already being used as an argument here, causing a conflict:

// Add a connect listener
io.on('connection', function (socket) {
    console.log('Client connected.');

    //when server receives message from client
    socket.on('message_from_browser', function (message) {
        console.log("Message from browser broadcasted: " + message.text);
        
        var updated_message = {
           text: message.text,
           port: PORT  
        };

        // send message to server B
        socket1.emit('server_message', updated_message);//send message to server B
    });

    // Disconnect listener
    socket.on('disconnect', function () {
        console.log('Client disconnected.');
    });
});

You also need to add listeners for incoming server messages for both socket1 and socket2.

io.on('connect', function(socket1){
    socket1.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM ANOTHER SERVER ON PORT '+ message.port + ": " + message.text);
    });
});

io.on('connect', function(socket2){
    socket2.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM ANOTHER SERVER ON PORT '+ message.port + ": " + message.text);
    });
});

Answer 3

Answer №2

Utilize a single variable and configurations to monitor multiple hosts, give this approach a try:

Revised version addressing various issues:

// Load prerequisites
var PORT = process.env.PORT || 8081; // modify port for alternative servers
var express = require("express");
var app = express();
var http = require("http").Server(app);
var io = require("socket.io")(http);
var async = require('async'); // optional dependency for this scenario ...
var client = require('socket.io-client');

app.use(express.static(__dirname + '/public'));

// store host details here ...
var otherServers = {
  server1: {
    url: 'http://localhost:8082'
  },
  server2: {
    url: 'http://localhost:8083'
  },
};

// Implement a connection listener
io.on('connection', function (socket) {
  console.log('Client connected.');
  
  // when the server receives a message from the client
  socket.on('message_from_browser', function (message) {
      console.log("Message broadcasted from browser: " + message.text);
      var updated_message = {
         text: message.text,
         port: PORT
      };

      // determine how the server will handle this message...
      // then send it
      otherServers.server1.client.broadcast.emit('server_message', updated_message);
  });

  // Disconnection listener
  socket.on('disconnect', function () {
      console.log('Client disconnected.');
  });
});

async.each(otherServers, function forEachOtherServer(otherServer, next) {
  // establish connection with another server
  otherServer.client = client.connect(otherServer.url, { reconnect: true });
  // perform additional operations if required for every client connection ...

  otherServer.client.on('connect', function (x) {

    otherServer.client.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM ANOTHER SERVER ON PORT '+ message.port + ": " + message.text);
        //socket.broadcast.emit('message_from_server', message_server);
    });
    console.log('Connected!');
  });

  next();
}, function afterConnectInAllServers(err) {
  if (err) throw err;
  // execute post-connection tasks on all servers ...
});

http.listen(PORT, function (req, res) {
  console.log("Server Started on port: " + PORT);
});

Answer 4

Utilize a single variable and configurations to monitor multiple hosts, give this approach a try:

Revised version addressing various issues:

// Load prerequisites
var PORT = process.env.PORT || 8081; // modify port for alternative servers
var express = require("express");
var app = express();
var http = require("http").Server(app);
var io = require("socket.io")(http);
var async = require('async'); // optional dependency for this scenario ...
var client = require('socket.io-client');

app.use(express.static(__dirname + '/public'));

// store host details here ...
var otherServers = {
  server1: {
    url: 'http://localhost:8082'
  },
  server2: {
    url: 'http://localhost:8083'
  },
};

// Implement a connection listener
io.on('connection', function (socket) {
  console.log('Client connected.');
  
  // when the server receives a message from the client
  socket.on('message_from_browser', function (message) {
      console.log("Message broadcasted from browser: " + message.text);
      var updated_message = {
         text: message.text,
         port: PORT
      };

      // determine how the server will handle this message...
      // then send it
      otherServers.server1.client.broadcast.emit('server_message', updated_message);
  });

  // Disconnection listener
  socket.on('disconnect', function () {
      console.log('Client disconnected.');
  });
});

async.each(otherServers, function forEachOtherServer(otherServer, next) {
  // establish connection with another server
  otherServer.client = client.connect(otherServer.url, { reconnect: true });
  // perform additional operations if required for every client connection ...

  otherServer.client.on('connect', function (x) {

    otherServer.client.on('server_message', function (message) {
        console.log('RECEIVED MESSAGE FROM ANOTHER SERVER ON PORT '+ message.port + ": " + message.text);
        //socket.broadcast.emit('message_from_server', message_server);
    });
    console.log('Connected!');
  });

  next();
}, function afterConnectInAllServers(err) {
  if (err) throw err;
  // execute post-connection tasks on all servers ...
});

http.listen(PORT, function (req, res) {
  console.log("Server Started on port: " + PORT);
});

Sending messages from one Socket.io server to another specific server

Answer №1

Answer №2

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