How to echo back the full sentence using node?

I would like to write a simple echo server in node. I am using the following

var net = require('net');

var server = net.createServer(function (socket) {
    socket.write('Echo server\r\n');
    socket.pipe(socket);
});

server.listen(8686, '127.0.0.1');

However this is not what I want. The code above will echo back every character.

what I want is echo back when I hit "return" key. How to implement that?