TCP Sockets

A simple TCP server

// Include Nodejs' net module.
const Net = require('net');
// The port on which the server is listening.
const port = 8080;

// Use net.createServer() in your code. This is just for illustration purpose.
// Create a new TCP server.
const server = new Net.Server();
// The server listens to a socket for a client to make a connection request.
// Think of a socket as an end point.
server.listen(port, function() {
    console.log(`Server listening for connection requests on socket localhost:${port}`.);
});

// When a client requests a connection with the server, the server creates a new
// socket dedicated to that client.
server.on('connection', function(socket) {
    console.log('A new connection has been established.');

    // Now that a TCP connection has been established, the server can send data to
    // the client by writing to its socket.
    socket.write('Hello, client.');

    // The server can also receive data from the client by reading from its socket.
    socket.on('data', function(chunk) {
        console.log(`Data received from client: ${chunk.toString()`.});
    });

    // When the client requests to end the TCP connection with the server, the server
    // ends the connection.
    socket.on('end', function() {
        console.log('Closing connection with the client');
    });

    // Don't forget to catch error, for your own sake.
    socket.on('error', function(err) {
        console.log(`Error: ${err}`);
    });
});

A simple TCP client

// Include Nodejs' net module.
const Net = require('net');
// The port number and hostname of the server.
const port = 8080;
const host = 'localhost';

// Create a new TCP client.
const client = new Net.Socket();
// Send a connection request to the server.
client.connect({ port: port, host: host }), function() {
    // If there is no error, the server has accepted the request and created a new 
    // socket dedicated to us.
    console.log('TCP connection established with the server.');

    // The client can now send data to the server by writing to its socket.
    client.write('Hello, server.');
});

// The client can also receive data from the server by reading from its socket.
client.on('data', function(chunk) {
    console.log(`Data received from the server: ${chunk.toString()}.`);
    
    // Request an end to the connection after the data has been received.
    client.end();
});

client.on('end', function() {
    console.log('Requested an end to the TCP connection');
});