Send Broadcast datagram

Question

I need to send a broadcast datagram to all machine (servers) connected to my network.

I'm using NodeJS Multicast

Client

var dgram = require('dgram');
var message = new Buffer("Some bytes");
var client = dgram.createSocket("udp4");
client.send(message, 0, message.length, 41234, "localhost");
// If I'm in the same machine 'localhost' works
// I need to do something 192.168.0.255 or 255.255.255
client.close();

Servers

 var dgram = require("dgram");

 var server = dgram.createSocket("udp4");

 server.on("message", function (msg, rinfo) {
   console.log("server got: " + msg + " from " +
     rinfo.address + ":" + rinfo.port);
 });

 server.on("listening", function () {
   var address = server.address();
   console.log("server listening " + address.address + ":" + address.port);
 });

 server.bind(41234);

Thanks.

Answer 1

I never used Node.js, but I do recall that with Berkely sockets (which seem to be the most widely used implementation of sockets) you need to enable the SO_BROADCAST socket option to be able to send datagrams to the broadcast address. Looking up the dgram documentation, there seems to be a function for it.

var client = dgram.createSocket("udp4");
client.setBroadcast(true);
client.send(message, 0, message.length, 41234, "192.168.0.255");

You might want to find out the broadcast address programmatically, but I can't help you with that.