Socket emit to room works for all sockets except the sender

Question

I'm creating a voting feature using socket.io. Sockets are placed into rooms by a channelId. Whenever any socket in the room emits a vote event, i'm trying to emit the current vote-list to all sockets in that room.

My problem is that if I have Sockets A, B, C in the same room, votes from Socket A are visible to B and C (that is, B and C's on.('vote') listeners are called), but NOT to A itself.

What i expect to happen, is that if Sockets A, B, C are in the same room, and A emits a vote, All sockets A, B, C vote listeners will be called.

Client:

These listeners are defined within methods, but i've singled them out for clarity. All variables are defined.

const socket = io('https://localhost:3001')

socket.emit('join-channel',{ 
    channelId: payload.channelId,
    senderId: socket.id
 })

socket.emit('vote',{
    senderId: socket.id,
    channelId: state.channelId,
    vote: payload.vote,
    userId: state.userId
})

socket.on(`vote`, function (data) {
    store.commit(MUTATIONS.SET_VOTES, data)
});

Server

module.exports = (app,server) => { var io = require('socket.io')(server);

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

    socket.on('join-channel',data=>{
        socket.join(data.channelId)
    })

    socket.on('vote',data=>{
        postVote(data)
        let { channelId } = data

        socket.to(channelId).emit(`vote`,STORE[channelId])
        //socket.emit(`vote`,STORE[channelId]) //My workaround so that the socket's messages are emitted back to itself
    })


});

};

My current workaround is to add socket.emit('vote',STORE[channelId]), so that it can emit data back to itself.

Answer 1

This is by design in the socket.io API. This form you were using:

socket.to(channelId).emit(...)

is specifically designed to send to all sockets in the channelId room EXCEPT socket.

If you want to send to ALL users in that room, then change the above code to:

io.to(channelId).emit(...)

---

Here's a quote from the socket.io doc for socket.to():

Sets a modifier for a subsequent event emission that the event will only be broadcasted to clients that have joined the given room (the socket itself being excluded).