1step.js

const net = require('net');

let port = 3000;
let isRoot = false;
const connectionList = new Map();
const expireDelta = 5*60*1000;

const server = net.createServer(socket => {
  socket.on('error', err => {
    console.log(err);
  });
  socket.on('data', function (data) {
    const str = data.toString();
    connectionList.set(JSON.parse(str), Date.now() + expireDelta);
    socket.write(connectionList.map(p => p.port).join(','));
  });
});

server.listen(port);

setInterval(checkExpire, 500)

server.on('error', err => {
  if (err.code === 'EADDRINUSE') {
    server.close();
    port += 1;
    server.listen(port);
  }
});

server.on('listening', () => {
  if (port === 3000) {
    isRoot = true;
    return;
  }

  connectRoot();
  connectPeers();

  client.on('data', function(data) {
    console.log('Connection list: ' + data);
  });

});

function checkExpire() {
  const now = Date.now();
  for (let [ port, exipireTime ] of connectionList.entries()) {
    if (exipireTime < now) {
      connectionList.delete(port);
    }
  }
}
function connectRoot() {
  const client = new net.Socket();
  client.connect(3000, '127.0.0.1', function() {
    console.log('Connected');
    client.write(JSON.stringify({ port }));
  });
}

function connectPeers() {
  const peerPorts = getNeighborsPorts(port);
  peerPorts.forEach(port => {
    const client = new net.Socket();
    client.connect(port, '127.0.0.1', () => {
      console.log('Connected to peer '+port);
    });
  });
}

function getNeighborsPorts(port) {
  let guess = port + 1;
  const ports = [];
  while (ports.length !== 3) {
    if (connectionList.has(guess)) {
      count++;
      ports.push(guess);
    } else {
      if (guess > port) {
        guess = port -1;
      } else {
        guess--;
      }
    }
  }
  return ports;
}