environment.js

exports.HOST = process.argv[2] || '127.0.0.1';
exports.PORT = process.argv[3] || 11111;

task1.js

var environment = require('./environment'),
    server = require('./tcp_echo_server'),
    createClient = require('./tcp_echo_client').createClient,
    HOST = environment.HOST,
    PORT = environment.PORT;


server.on('connection', function (socket) {
    server.close();
    socket.end();
});

server.listen(PORT, HOST, function () {
    createClient(PORT, HOST);
});

task2.js

var environment = require('./environment'),
    server = require('./tcp_echo_server'),
    createClient = require('./tcp_echo_client').createClient,
    HOST = environment.HOST,
    PORT = environment.PORT,
    MAX_CONNECTIONS = 10,
    count = 1000;


function _createClient() {
    var client = createClient(PORT, HOST);

    client.on('close', function (error) {
        if (count) {
            _createClient();
        }
    });
}

server.maxConnections = MAX_CONNECTIONS;

server.on('connection', function (socket) {
    if (!--count) {
        server.close();
    }
    socket.end();
});

server.listen(PORT, HOST, function () {
    for (var i = 0; i < MAX_CONNECTIONS; i++) {
        _createClient();
    }
});

tcp_echo_client.js

var net = require('net'),
    readline = require('readline'),
    environment = require('./environment'),
    clients = {},
    rl;


function createClient(port, host) {
    var options = {
            host: host || environment.HOST,
            port: port || environment.PORT,
            toString: function () {
                return this.host + ':' + this.port;
            }
        },
        client = net.connect(options),
        key;

    client.on('error', function (e) {
        console.error('Connection Failed - ' + options);
        console.error(e.message);
    });

    client.on('connect', function () {
        var addr = client.address();

        console.log('Connected - ' + options);
        key = addr.address + ':' + addr.port;
        clients[key] = client;
    });

    client.on('data', function (chunk) {
        process.stdout.write(chunk.toString());
    });

    client.on('end', function (error) {
        console.log('Connection End - ' + options);
        delete clients[key];
    });

    client.on('close', function (error) {
        console.log('Client Closed');
    });

    return client;
}

exports.createClient = createClient;


rl = readline.createInterface(process.stdin, process.stdout);
rl.on('SIGINT', function () {
    for (key in clients) {
        clients[key].end();
    }

    rl.close();
});


function main() {
    var client = createClient(),
        i = 0;

    client.setTimeout(1000);

    client.on('timeout', function () {
        var str = i + ': Hello World\n';

        process.stdout.write('[S] ' + str);
        client.write(str);
        i++;
    });

    client.on('end', function (error) {
        client.setTimeout(0);
    });
}

if (require.main === module) {
    main();
}

tcp_echo_server.js

var net = require('net'),
    readline = require('readline'),
    server = net.createServer(),
    clients = {},
    rl;


module.exports = server;
server.maxConnections = 3;

function connectionStatus() {
    return server.connections + '/' + server.maxConnections;
}


function Client(socket) {
    this.socket = socket;
}

Client.key = function (socket) {
    return socket.remoteAddress + ':' + socket.remotePort;
};

Client.prototype.writeData = function (data) {
    var socket = this.socket;

    if (socket.writable) {
        process.stdout.write('[' + this.key + '] - ' + data);
        socket.write('[R] ' + data);
    }
};

Object.defineProperty(Client.prototype, 'key', {
    get: function () {
        return this.constructor.key(this.socket);
    }
});


server.on('listening', function () {
    var addr = server.address();

    console.log('Listening Start on Server - ' + addr.address + ':' + addr.port);
});

server.on('connection', function (socket) {
    var client = new Client(socket),
        key = client.key,
        status = connectionStatus();

    console.log('Connection Start(' + status + ') - ' + key);
    clients[key] = client;
});

server.on('connection', function (socket) {
    var key = Client.key(socket),
        data = '',
        newline = /\r\n|\n/;

    socket.on('data', function (chunk) {
        data += chunk.toString();

        if (newline.test(data)) {
            clients[key].writeData(data);
            data = '';
        }
    });
});

server.on('connection', function (socket) {
    var key = Client.key(socket);

    socket.on('end', function () {
        var status = connectionStatus();

        console.log('Connection End(' + status + ') - ' + key);
        delete clients[key];
    });
});

server.on('close', function () {
    console.log('Server Closed');
    rl.close();
});


rl = readline.createInterface(process.stdin, process.stdout);
rl.on('SIGINT', function () {
    var socket, key;

    // stop accepting new clients first
    server.close();

    for (key in clients) {
        socket = clients[key].socket;
        socket.end();
    }

    rl.close();
});


function main() {
    var environment = require('./environment');
    server.listen(environment.PORT, environment.HOST);
}

if (require.main === module) {
    main();
}