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Hi all and thanks for your time and your help.

I need a simple example for use socket.io-redis, with comments please. I read the documentation, but I did not understand. Thank you,

Rifton007
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2 Answers2

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The socket.io-redis documentation don't mention you actually need to run a redis server so you might have forgotten that. The socket.io-redis plugin uses the pub/sub client of the redis server to connect multiple socket.io instances.

  1. download and install a redis server from https://redis.io

  2. add the redis plugin to your socket.io instances:

    var express = require('express');
var app = express();
var server = require('http').Server(app);
var io = require('socket.io')(server);
var redis = require('socket.io-redis');
io.adapter(redis({ host: 'localhost', port: 6379 }));

    The 6379 is the default redis port, localhost if you run node and redis on the same server.

  3. add socket.io and socket.io-redis functions you need

    var your_namespace_socket = io.of('/your-namespace');
your_namespace_socket.on('connection', function(socket){

  socket.on('join', function(room){
    socket.join(room);

    //log other socket.io-id's in the room
    your_namespace_socket.adapter.clients([room], (err, clients) => {
      console.log(clients);
    });
  });
});

  4. Start the server with socket.io

    server.listen(3000, function(){
   logger.debug('listening on *:3000');
});
Dries Cleymans
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    If I ran multiple sockeio nodejs server in different machine, will this adaptor allow me to join selected users, from different servers, in a single room? – Aedric Dec 04 '19 at 02:53
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    @Aedric yes it will! The room itself is persisted on Redis so when you ask for users, you don't actually ask it from the server (in-memory), but from Redis (persisted across servers). From the package's GitHub page - "Adapter to enable broadcasting of events to multiple separate socket.io server nodes." – kano Mar 27 '20 at 08:17
  • Thanks a lot. Why nobody tell that we need a redis server? Accutally there are a lot of people just starting who never heard about redis that really can't understand this necessity. Again, thanks a lot – Leonardo Rick Feb 28 '21 at 23:02
  • @kano From the Github page - Note: no data is stored in Redis itself. Redis server only acts as a pub/sub server. Each emitted message is published to redis which is broadcast to other socket servers as well. – zahlen Mar 01 '21 at 09:13
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io.on('connect', socket => {
    socket.on("createNotifications", () => {
        io.sockets.emit("notificationCreated", {
            'id': Date.now(),
            'name': `You just created notification at date`
        });
    });
});
Ankur Shukla
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