Socket.io send data only a client who make request
I assume that in the post method you have identified the user or session.
So you can create a room per user to later emit on it.
client.js
var room = "#usernameRoom";socket.on('connect', function() { socket.emit('privateroom', room);});socket.on('privatemessage', function(data) { console.log('Incoming private message:', data);});server.js
io.sockets.on('connection', function(socket) { var socket_room; socket.on('privateroom', function(room) { socket_room = room; socket.join(room); }); socket.on('disconnect', function() { if (socket_room) { socket.leave(socket_room); } });});app.post(.....){ myModel.save(function (err) { if (err) return handleError(err); ///send to all io.sockets.emit("ev", { ...... }); //// send to one client // now, it's easy to send a message to just the clients in a given private room privateRoom = "#usernameRoom"; io.sockets.in(privateRoom ).emit('privatemessage', 'Never reveal your identity!'); });}hope that helps