[node.js] Socket.IO - how do I get a list of connected sockets/clients?

I'm trying to get a list of all the sockets/clients that are currently connected.

io.sockets does not return an array, unfortunately.

I know I could keep my own list using an array, but don't think this is an optimal solution for 2 reasons:

1. Redundancy. Socket.IO already keeps a copy of this list.

2. Socket.IO provides method to set arbitrary field values for clients (i.e: socket.set('nickname', 'superman')) so I'd need to keep up with these changes if I were to maintain my own list.

Help?

This is the best way to access it in socket.io 1.3

Object.keys(socket.adapter.rooms[room_id])

[email protected]

I used Object.Keys to get the array of socket connected. Then in the same array iterate with map function to build a new array of objects

var connectedUsers = Object.keys(io.sockets.connected).map(function(socketId) {
    return { socket_id : socketId, socket_username: io.sockets.connected[socketId].username };
});

// test
console.log(connectedUsers);

Perhaps this answer can help to get socket id/username array.

Socket.io 1.7.3(+) :

function getConnectedList ()
{
    let list = []
    
    for ( let client in io.sockets.connected )
    {
        list.push(client)
    }
    
    return list
}

console.log( getConnectedList() )

// returns [ 'yIfhb2tw7mxgrnF6AAAA', 'qABFaNDSYknCysbgAAAB' ]

For anyone that just wants a COUNT of the connected clients I believe this will do it:

io.sockets.manager.server.connections

For cluster mode, using redis-adaptor

io.in(<room>).clients(function(err, clients) {

});

As each socket is itself a room, so one can find whether a socket exist using the same.

Very simple in socket.io 1.3:

io.sockets.sockets - is an array containing the connected socket objects. If you stored the username in each socket, you can do:

io.sockets.sockets.map(function(e) {
    return e.username;
})

Boom. You have the names of all connected users.

Using Socket.IO 1.x:

Get array of the connected clients:

io.engine === io.eio // => true
Object.keys(io.engine.clients) // => [ 'US8AxrUrrDF_G7ZUAAAA', 'Ov2Ca24Olkhf2NHbAAAB' ]
Object.keys(io.eio.clients)    // => [ 'US8AxrUrrDF_G7ZUAAAA', 'Ov2Ca24Olkhf2NHbAAAB' ]

Get the number of connected clients:

io.engine.clientsCount // => 2
io.eio.clientsCount    // => 2

[email protected]

 io.in('room1').sockets.sockets.forEach((socket,key)=>{
        console.log(socket);
    })

all socket instance in room1

Version +2.0

In version +2.0 you specify the namespace/room/node you are querying against.

As with broadcasting, the default is all clients from the default namespace ('/'):

const io = require('socket.io')();  
io.clients((error, clients) => {
      if (error) throw error;
      console.log(clients); // => [6em3d4TJP8Et9EMNAAAA, G5p55dHhGgUnLUctAAAB]
});

Gets a list of client IDs connected to specific namespace (across all nodes if applicable).

const io = require('socket.io')();
io.of('/chat').clients((error, clients) => {
     if (error) throw error;
     console.log(clients); // => [PZDoMHjiu8PYfRiKAAAF, Anw2LatarvGVVXEIAAAD]
});

An example to get all clients in namespace's room:

const io = require('socket.io')();
io.of('/chat').in('general').clients((error, clients) => {
      if (error) throw error;
      console.log(clients); // => [Anw2LatarvGVVXEIAAAD] 
});

This is from the official documentation: Socket.IO Server-API

I see a lot of good answers here and many where quite useful but not quite what I needed. I am using sockets for a pubsub feature in which an interested client can listen to any changes in a given record.

My specific issue was that the same socket was joining the same room several times. The solution to this was to check if the socket had the room inside its rooms property already.

var room = myObj.id.toString();
if (socket.rooms.indexOf(room) === -1) {
    socket.join(room);
    socket.emit('subscribed', {to : room});
} else {
    console.log("Already in room");
}

Hope this helps someone.

In Socket.IO 1.4

To get the array of All connected Users :

var allConnectedClients = Object.keys(io.sockets.connected);// This will return the array of SockeId of all the connected clients

To get the Count of all clients :

var clientsCount = io.engine.clientsCount ; // This will return the count of connected clients

I believe you can access this from the socket's manager property?

var handshaken = io.manager.handshaken;
var connected = io.manager.connected;
var open = io.manager.open;
var closed = io.manager.closed;

As of version 1.5.1, I'm able to access all the sockets in a namespace with:

var socket_ids = Object.keys(io.of('/namespace').sockets);
socket_ids.forEach(function(socket_id) {
    var socket = io.of('/namespace').sockets[socket_id];
    if (socket.connected) {
        // Do something...
    }
});

For some reason, they're using a plain object instead of an array to store the socket IDs.

I've gone through this pain today. Socket.io will be much better if they could make a proper documentation for their API.

Anyway, I tried to look into io.sockets and found a number of options we can use:

io.sockets.connected //Return {socket_1_id: {}, socket_2_id: {}} . This is the most convenient one, since you can just refer to io.sockets.connected[id] then do common things like emit()
io.sockets.sockets //Returns [{socket_1}, {socket_2}, ....]. Can refer to socket_i.id to distinguish
io.sockets.adapter.sids //Return {socket_1_id: {}, socket_2_id: {}} . Looks similar to the first one but the object is not actually the socket, just the information.

// Not directly helps but still relevant
io.sockets.adapter.rooms //Returns {room_1_id: {}, room_2_id: {}}
io.sockets.server.eio.clients //Return client sockets
io.sockets.server.eio.clientsCount //Return number of connected clients

Also, do note that when using socket.io with namespace, the above methods will break since io.sockets becomes an array instead of an object. To resolve, just replace io.sockets by io (i.e io.sockets.connected becomes io.connected, io.sockets.adapter.rooms becomes io.adapter.rooms ...)

Tested on socket.io 1.3.5

For version 2.3 this works and it will get you the socket too, it seems to me that socketIo is changing too fast and to much with to little readable documentation after using it for a while.

ioSite.of('/').in(roomId).clients((error, clients) => {
    if (error) throw error;
    for (var i=0;i<clients.length;i++) {
        clientId=clients[i];
        console.log(clientId);

        // load the socket of your namespace
        var socket=ioSite.of('/').in(roomId).connected[clientId]
        console.log(socket.constructor.name);
        console.log(socket.id);
    }
});

still this does not feel right, as I have always this feeling with socket Io somehow

Socket.io 1.4.4

Sample code for you.

function get_clients_by_room(roomId, namespace) {
        io.of(namespace || "/").in(roomId).clients(function (error, clients) {
            if (error) { throw error; }
            console.log(clients[0]); // => [Anw2LatarvGVVXEIAAAD]
            console.log(io.sockets.sockets[clients[0]]); //socket detail
            return clients;
        });
    }

I think will help someone this code block.

Socket.io 1.4

Object.keys(io.sockets.sockets); gives you all the connected sockets.

Socket.io 1.0 As of socket.io 1.0, the actual accepted answer isn't valid anymore. So I made a small function that I use as a temporary fix :

function findClientsSocket(roomId, namespace) {
    var res = []
    // the default namespace is "/"
    , ns = io.of(namespace ||"/");

    if (ns) {
        for (var id in ns.connected) {
            if(roomId) {
                var index = ns.connected[id].rooms.indexOf(roomId);
                if(index !== -1) {
                    res.push(ns.connected[id]);
                }
            } else {
                res.push(ns.connected[id]);
            }
        }
    }
    return res;
}

Api for No namespace becomes

// var clients = io.sockets.clients();
// becomes : 
var clients = findClientsSocket();

// var clients = io.sockets.clients('room');
// all users from room `room`
// becomes
var clients = findClientsSocket('room');

Api for a namespace becomes :

// var clients = io.of('/chat').clients();
// becomes
var clients = findClientsSocket(null, '/chat');

// var clients = io.of('/chat').clients('room');
// all users from room `room`
// becomes
var clients = findClientsSocket('room', '/chat');

Also see this related question, in which I give a function that returns the sockets for a given room.

function findClientsSocketByRoomId(roomId) {
var res = []
, room = io.sockets.adapter.rooms[roomId];
if (room) {
    for (var id in room) {
    res.push(io.sockets.adapter.nsp.connected[id]);
    }
}
return res;
}

Socket.io 0.7

API for no namespace:

var clients = io.sockets.clients();
var clients = io.sockets.clients('room'); // all users from room `room`

For a namespace

var clients = io.of('/chat').clients();
var clients = io.of('/chat').clients('room'); // all users from room `room`

Note: Since it seems the socket.io API is prone to breaking, and some solution rely on implementation details, it could be a matter of tracking the clients yourself:

var clients = [];

io.sockets.on('connect', function(client) {
    clients.push(client); 

    client.on('disconnect', function() {
        clients.splice(clients.indexOf(client), 1);
    });
});

v.10

var clients = io.nsps['/'].adapter.rooms['vse'];
/* 
'clients' will return something like:
Room {
sockets: { '3kiMNO8xwKMOtj3zAAAC': true, FUgvilj2VoJWB196AAAD: true },
length: 2 }
*/
var count = clients.length;  // 2
var sockets = clients.map((item)=>{  // all sockets room 'vse'
       return io.sockets.sockets[item];
      });
sample >>>
var handshake  = sockets[i].handshake; 
handshake.address  .time .issued ... etc.

I think we can access the socket object from the server, and you can assign the nickname, and point its socket id,

io.sockets.on('connection',function(socket){ 
    io.sockets.sockets['nickname'] = socket.id;
    client.on("chat", function(data) {      
        var sock_id = io.sockets.sockets['nickname']
        io.sockets.sockets[sock_id].emit("private", "message");
    });    
});

On disconnect please remove the nickname from io.sockets.sockets.

on socket.io 1.3 i've accomplished this in 2 lines

var usersSocketIds = Object.keys(chat.adapter.rooms['room name']);
var usersAttending = _.map(usersSocketIds, function(socketClientId){ return chat.connected[socketClientId] })

As of socket.io 1.5, note the change from indexOf which appears to de depreciated, and replaced by valueOf

function findClientsSocket(roomId, namespace) {
    var res = [];
    var ns = io.of(namespace ||"/");    // the default namespace is "/"

    if (ns) {
        for (var id in ns.connected) {
            if (roomId) {
                //var index = ns.connected[id].rooms.indexOf(roomId) ;
                var index = ns.connected[id].rooms.valueOf(roomId) ; //Problem was here

                if(index !== -1) {
                    res.push(ns.connected[id]);
                }
            } else {
                res.push(ns.connected[id]);
            }
        }
    }
    return res.length;
}

For socket.io version 2.0.3, the following code works:

function findClientsSocket(io, roomId, namespace) {
    var res = [],
        ns = io.of(namespace ||"/");    // the default namespace is "/"

    if (ns) {
        for (var id in ns.connected) {
            if(roomId) {
                // ns.connected[id].rooms is an object!
                var rooms = Object.values(ns.connected[id].rooms);  
                var index = rooms.indexOf(roomId);
                if(index !== -1) {
                    res.push(ns.connected[id]);
                }
            }
            else {
                res.push(ns.connected[id]);
            }
        }
    }
    return res;
}

If the project has a socket.io cluster this means socket.io-redis adapter is being used.

If the case like the above, getting the all connected sockets id process must be applied via socket.io-redis adapter. The examples below might be used for this;

io.of('/').adapter.clients(function (err, clients) {
  console.log("clients: ", clients); // an array containing all connected socket ids
});


io.of('/').adapter.allRooms(function (err, rooms) {
  console.log("all rooms: ", rooms);
});

Please visit socket.io-redis github page for more details.

Here is a quick way to convert the hash of connected sockets from a namespace into an array using ES6 generators (applies to socket.io >= v1.0.0):

io.on('connection', function(socket) {
  var hash = io.of('/').connected
  var list = null

  hash[Symbol.iterator] = function*() {
    // for..of loop to invoke Object.keys() default iterator
    // to get the array values instead of the keys
    for(var id of Object.keys(hash)) yield hash[id]
  }

  list = [...hash]
  console.log(Array.isArray(list)) // true
})

After socket.io 1.0 we cannot use

io.sockets.clients(); 
or
io.sockets.clients('room'); 

anymore. Instead you can use the following

var clients_in_the_room = io.sockets.adapter.rooms[roomId]; 
for (var clientId in clients_in_the_room ) {
  console.log('client: %s', clientId); //Seeing is believing 
  var client_socket = io.sockets.connected[clientId];//Do whatever you want with this
}

I don't know if this is still going. But something like this is what I ended up using (I keep a session object on each connected socket, which in turn contains the username and other info:

var connectedUsers = Object.keys(io.sockets.connected).map(function(socketId) {
    return io.sockets.connected[socketId].session.username;
});

This is the simplest way in Socket.IO 1.0+, if you are not using namespaces or rooms.

io.nsps["/"].sockets.length

This looks at the default namespace and determines the length of the sockets array, without needing to use Object.keys()