doorbell.js

var os=require('os');
var net=require('net');
var Gpio = require("onoff").Gpio;
var networkInterfaces=os.networkInterfaces();
var port = 8081;
var sockets = [];

var cols = [
	new Gpio(7, 'in', 'both'),
	new Gpio(8, 'in', 'both'),
	new Gpio(25, 'in', 'both'),
	new Gpio(24, 'in', 'both'),
	new Gpio(23, 'in', 'both')
];

var rows = [
	new Gpio(14, 'out'),
	new Gpio(15, 'out'),
	new Gpio(18, 'out')
];

setInterval(function() {
	var result = readButtonMatrix();

	if (result) {
		console.log(result.toString());

		for (var i in sockets) {
			sockets[i].write(result+'\n');
		}
	};

},100);

function readButtonMatrix() {
	var s = '';
	for (var kolom=0; kolom<cols.length; kolom++) {
		for (var specifiek=0; specifiek<rows.length; specifiek++) {
			for (var i=0; i<rows.length; i++) {
				rows[i].writeSync(1);
			}
			rows[specifiek].writeSync(0);
			//console.log(cols[kolom].readSync() + " ");
			var value = cols[kolom].readSync();
			s = s + value;

			if (value==0) return [kolom,specifiek];
			//console.log(kolomnummertje.join(','));
		}
		//console.log("- ");
		s = s + " - ";
	}
	//console.log(s);
	return null;
}

function callback_server_connection(socket){
  var remoteAddress = socket.remoteAddress;
  var remotePort = socket.remotePort;

  socket.setNoDelay(true);
  console.log("connected: ", remoteAddress, " : ", remotePort);
  sockets.push(socket);

  socket.on('data', function (data) {
    //op deze plek ontvangt de server van 1 client een berichtje
    //hier het berichtje doorsturen naar alle andere clients
    for (var i in sockets) {
			console.log('fwd to:',i,data.toString());
			sockets[i].write(data.toString());
		}
  });

  socket.on('end', function () {
    console.log("ended: ", remoteAddress, " : ", remotePort);
    for (var i in sockets) {
			if (sockets[i]==socket) {
				sockets.splice(i,1); //remove socket from array
			}
		}
  });
}

console.log("node.js net server is waiting:");
for (var interface in networkInterfaces) {
  networkInterfaces[interface].forEach(function(details){
    if ((details.family=='IPv4') && !details.internal) {
      console.log(interface, details.address);
    }
 });
}
console.log("port:", port);

var netServer = net.createServer(callback_server_connection);
netServer.listen(port);