 <p>If somehow you can store the socektID of the sender in a variable, then you can emit to that particular client in app.post method. Do something like this:</p> <pre><code>var id; io.sockets.on('connection', function(socket){ socket.on('some event'){ id = socket.id; } }); </code></pre> <p>and do this in app.post method:</p> <pre><code>app.post('/room', function(req, res) { io.sockets.socket(socketid).emit('event name', {data: yourData}); }); </code></pre> <p>Though I've proposed this solution but your approach doesn't seem too convincing.</p>