Node.js: client doesn't die when TCP connection closes

Question

I built a simple TCP server and a simple TCP client in Node.js

Now, when the client sends "exit" to the server, the connection is successfully closed. The server deletes the socket from its sockets list and sends "Bye bye!" to the client.

The connection on the client is closed as well but the app is still waiting for other inputs, so it doesn't die and I'm forced to type CTRL+C.

I tried adding process.exit() after connection closes but it doesn't work:

CLIENT CODE:

var net = require('net'),
    config = require(__dirname + '/config.json'),
    connection = net.createConnection(config.port, config.host);

connection.setEncoding('utf8');

connection.on('connect', function () {
    console.log('Connected');
});

connection.on('error', function (err) {
    console.error(err);
});

connection.on('data', function (data) {
    console.log('» ' + data);
});

connection.on('close', function() {
    console.log('Connection closed');
});

process.stdin.on('data', function (data) {

    if ((new String(data)).toLowerCase() === 'exit') {
        connection.end();
        process.exit();
    }
    else {
        connection.write(data);
    }

});

process.stdin.resume();

SERVER CODE:

var server = require('net').createServer(),
    config = require(__dirname + '/config.json'),
    sockets = [];

server.on('connection', function (socket) {
    socket.setEncoding('UTF-8');

    socket.on('data', function (data) {

        console.log('Received data: ' + data);

        if (data.trim().toLowerCase() === 'exit') {
            socket.write("Bye bye!\n");
            socket.end();
        }
        else {
            sockets.forEach(function (client) {
                if (client && client != socket) {
                    client.write(data);
                }
            });
        }

    });

    socket.on('close', function () {
        console.log('Connection closed');
        sockets.splice(sockets.indexOf(socket), 1);

        console.info('Sockets connected: ' + sockets.length);
    });

    sockets.push(socket);
});

server.on('listening', function () {
    console.log('Server listening');
});

server.on('close', function () {
    console.log('Server is now closed');
});

server.on('error', function (err) {
    console.log('error:', err);
});

server.listen(config.port);

EDIT:

I added a client connection "on close" event handler. So, the string "Connection closed" is now printed by the server and by the client too.

Answer 1

I think you're looking for this: socket.unref().

From Node.js documentation (https://nodejs.org/api/net.html#net_socket_unref):

socket.unref()#

Calling unref on a socket will allow the program to exit if this is the only active socket in the event system. If the socket is already unrefd calling unref again will have no effect.

Answer 2

Some time ago when improving the tests suite for node-cubrid module, I had encountered the same problem. After all tests have passed, nodeunit process didn't quit because node-cubrid was using connection.end() to close the client socket when timeout occurs, just like you did.

Then I replaced connection.end() with connection.destroy(), a cleaner way to ensure the socket is really closed without actually terminating the running process, which, I think, is a better solution than the above suggested process.exit(). So, in your client code context, I would do:

process.stdin.on('data', function (data) {
    if ((new String(data)).toLowerCase() === 'exit') {
       connection.destroy();
    }
    else {
       connection.write(data);
    }
});

According to Node.js documentation:

socket.destroy()

Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).