node js example to demonstrate socket lifecycle events

self-destruct-server.js

const net = require('net');
const { spawn } = require('child_process');

const HOST = '127.0.0.1';
const PORT = 6969;

// Server /////
const _logServer = (p) => (s) => console.log(`[Server:${p}]`, s);
const logServer = _logServer('main');

const server = net.createServer();
server.listen(PORT, HOST, () => {
  const info = server.address();
  logServer(`Server listening on ${info.address}:${info.port}`);
});

const setupSocket = (sock, logServer, shouldClose=false) => {
  sock.on('data', data => {        
    logServer(`DATA ${sock.remoteAddress}:${data}`);
    // Echo data back to the socket
    sock.write(`You said "${data}"`);
    if(shouldClose) {
      logServer('Ending socket')
      sock.end()
    }
  });

  sock.on('end', data => {
    logServer(`FIN received: ${sock.remoteAddress} ${sock.remotePort}`);
  });  

  sock.on('close', data => {
    logServer(`CLOSED: ${sock.remoteAddress} ${sock.remotePort}`);
  });  
}

let count = 0;
server.on('connection', sock => {
  count += 1;
  const logServer = _logServer(`${count}`);
  logServer(`CONNECTED: ${count}`);
  setupSocket(sock, logServer, count == 3); 
});

server.on('end', () => logServer('client disconnected'));
server.on('error', error => logServer(error));

// Client /////
const _logClient = (p) => (s) => console.log(`[Client:${p}]`, s);

const createClient = (name, destroy=true, host, port) => {
  const logClient = _logClient(name);

  const client = new net.Socket();
  logClient('Created');
  
  // Timeout after 3s of inactivity on socket
  client.setTimeout(3000);

  client.on('data', data => {  
    logClient('DATA: ' + data);
    
    if(destroy) {
      logClient('self destruct')
      client.destroy();
    }
  });
  
  client.on('end', () => {
    logClient('Connection ended');
  });

  client.on('error', err => {
    logClient(err);
  });

  client.on('timeout', () => {
    logClient(`timed out`)
    client.end();
  });

  client.on('close', () => {
    logClient('Connection closed');
  });

  client.on('connect', () => {
    logClient(`CONNECTED TO: ${host}:${port}`);
    client.write('I am Chuck Norris!');
  });  

  client.connect(port, host);

  return client;
}

// Spawn server that we will terminate after client connects
const explode = spawn('node', ['self-destruct-server.js']);
explode.on('error', error => {
  console.log(error);
});

setTimeout(() => {
  console.log("Explode server");
  explode.kill('SIGTERM');
}, 1500);


const c1 = createClient('c1', true, HOST, PORT);
const c2 = createClient('c2', false, HOST, PORT);
const c3 = createClient('c3', false, HOST, PORT);
// Note: Must wait ~ 20s for c4 to timeout
const c4 = createClient('c4', false, '12.34.56.78', 1234); // ETIMEDOUT
const c5 = createClient('c5', false, HOST, 8000); // ECONNRESET
const c6 = createClient('c6', false, HOST, 8001); // ECONNREFUSED

socket-lifecycle.js

const net = require('net');
const { spawn } = require('child_process');

const HOST = '127.0.0.1';
const PORT = 6969;

// Server /////
const _logServer = (p) => (s) => console.log(`[Server:${p}]`, s);
const logServer = _logServer('main');

const server = net.createServer();
server.listen(PORT, HOST, () => {
  const info = server.address();
  logServer(`Server listening on ${info.address}:${info.port}`);
});

const setupSocket = (sock, logServer, shouldClose=false) => {
  sock.on('data', data => {        
    logServer(`DATA ${sock.remoteAddress}:${data}`);
    // Echo data back to the socket
    sock.write(`You said "${data}"`);
    if(shouldClose) {
      logServer('Ending socket')
      sock.end()
    }
  });

  sock.on('end', data => {
    logServer(`FIN received: ${sock.remoteAddress} ${sock.remotePort}`);
  });  

  sock.on('close', data => {
    logServer(`CLOSED: ${sock.remoteAddress} ${sock.remotePort}`);
  });  
}

let count = 0;
server.on('connection', sock => {
  count += 1;
  const logServer = _logServer(`${count}`);
  logServer(`CONNECTED: ${count}`);
  setupSocket(sock, logServer, count == 3); 
});

server.on('end', () => logServer('client disconnected'));
server.on('error', error => logServer(error));

// Client /////
const _logClient = (p) => (s) => console.log(`[Client:${p}]`, s);

const createClient = (name, destroy=true, host, port) => {
  const logClient = _logClient(name);

  const client = new net.Socket();
  logClient('Created');
  
  // Timeout after 3s of inactivity on socket
  client.setTimeout(3000);

  client.on('data', data => {  
    logClient('DATA: ' + data);
    
    if(destroy) {
      logClient('self destruct')
      client.destroy();
    }
  });
  
  client.on('end', () => {
    logClient('Connection ended');
  });

  client.on('error', err => {
    logClient(err);
  });

  client.on('timeout', () => {
    logClient(`timed out`)
    client.end();
  });

  client.on('close', () => {
    logClient('Connection closed');
  });

  client.on('connect', () => {
    logClient(`CONNECTED TO: ${host}:${port}`);
    client.write('I am Chuck Norris!');
  });  

  client.connect(port, host);

  return client;
}

// Spawn server that we will terminate after client connects
const explode = spawn('node', ['self-destruct-server.js']);
explode.on('error', error => {
  console.log(error);
});

setTimeout(() => {
  console.log("Explode server");
  explode.kill('SIGTERM');
}, 1500);


const c1 = createClient('c1', true, HOST, PORT);
const c2 = createClient('c2', false, HOST, PORT);
const c3 = createClient('c3', false, HOST, PORT);
const c4 = createClient('c4', false, '12.34.56.78', 1234);
const c5 = createClient('c5', false, HOST, 8000);