Sending data to specific user via node.js and socket.io

In referrer to node.js routing data with socket.io

On client:

 // send data on some event
 socket.emit('send', { u: user_id, a: action, v: value });

I have user_id and i could add user_id sender

On server:

socket.on('send', function (data) {
    socket.broadcast.emit('request', { request: data });
});

Now the data is sent to all users listening to port, but I would like to only 2 by 2 users can get data.

So, users 1 & 2 are having there "channel", and users 3 & 4 theirs.

You need the id of the socket (socket.id) you want to send the request. Probably you will need an array with the user_id and its socketID (you can save it when the user enters). Then, when you know the socket id, you can send a message only to this socket.

io.sockets.socket(socketID).emit('request', { request: data });