Node.js TCP Socket - if either of them breaks, they'll keep trying to reconnect

client.js

var net = require('net');

//
// Client
//

function openSocket() {
    var socket = net.connect(3e3);
    socket.setKeepAlive(true);
    socket.on('connect', onConnect.bind({}, socket));
    socket.on('error', onError.bind({}, socket));
}

var interval;
function onConnect(socket) {

    console.log('Socket is open!');

    interval = setInterval(function() {
        var msg = parseInt(+new Date) + '';
        socket.write(msg, function() {
            console.log('Sent:', msg);
        });
    }, 500);
}

function onError(socket) {

    console.log('Socket error!');

    // Kill socket
    clearInterval(interval);
    socket.destroy();
    socket.unref();

    // Re-open socket
    setTimeout(openSocket, 1e3);
}

openSocket();

server.js

var net = require('net');

//
// Server
//

var server = new net.Server();

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

    console.log('Socket is open!');

    socket.setEncoding('utf8');
    socket.on('data', function(data) {
        console.log('Received:', data);
    });

    socket.on('error', function() {
        console.log('Socket error!');
    });
});

server.listen(3e3, function() {
    console.log('Server is listening!');
});

Excellent example, thanks very much !

This is helpful, thank you good sir

How to determine that a client has disconnected / not connected to the server any more ?
And we are trying to write to the socket ?
How to determine this without waiting for timeout of the socket ?

How to determine that a client has disconnected / not connected to the server any more ?
And we are trying to write to the socket ?
How to determine this without waiting for timeout of the socket ?

If client closed connection correctly (by end() ), socket.close() will be fired immediately.
Otherwise you need to write your own ACK system for each message, and to not send new portion of data while you not received ACK.

This doesn't work for me.

Pulling the network cable out and back in causes: "ECONNRESET".
And causes [ERR_STREAM_DESTROYED]: Cannot call write after a stream was destroyed (for each time you try to write).

And then for each time you try to write; starts a new connection; but for some reason doesn't continue gracefully.
Also; it doesn't even print the actual error.

Printing the error is a simple fix. in the 'error' listener; change the console log to 'console.log(error);' this will output the error instead of the verbiage he has written.