[dgram]no udp multicast message received when binding on a specific address

[tberthe]

When binding a dgram udp socket on a specific address my program does not receive any multicast message.
Here are 3 programs that demonstrate the problem:

receive-all-addresses.js

var dgram = require('dgram');
var s = dgram.createSocket('udp4');

var MULTICAST_IP = "225.0.0.1"

s.bind(8001, function() {
  s.addMembership(MULTICAST_IP);
  console.log("listening on all addresses");
});

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

receive-specific-address.js

var dgram = require('dgram');
var s = dgram.createSocket('udp4');

var MULTICAST_IP = "225.0.0.1"
var LOCAL_IP     = "10.80.10.23"

s.bind(8001, LOCAL_IP, function() {
  s.addMembership(MULTICAST_IP);
  console.log("listening on a specific address");
});

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

send.js

var dgram = require('dgram');
var s = dgram.createSocket('udp4');
var MULTICAST_IP = "225.0.0.1"
var LOCAL_IP     = "10.80.10.23"

s.bind(8000);

function sendDirectHello(s)
{
  var b = new Buffer("Direct Hello!");
  s.send(b, 0, b.length, 8001, LOCAL_IP, function(err, bytes) {
    console.log("Sent " + bytes + " bytes");
    s.close();
  });
}

function sendMulticastThenDirectHello(s)
{
  var b = new Buffer("Multicast Hello!");
  s.send(b, 0, b.length, 8001, MULTICAST_IP, function(err, bytes) {
    console.log("Sent " + bytes + " bytes");
    sendDirectHello(s);
  });
}

sendMulticastThenDirectHello(s);

When listening on all addresses the program receives both messages from send.js:

pi@raspberrypi-js ~/udp_multicast $ iojs receive-all-addresses.js
listening on all addresses
server got: Multicast Hello! from 10.80.10.23:8000
server got: Direct Hello! from 10.80.10.23:8000

but when listening on a single address the program only receives the direct message:

pi@raspberrypi-js ~/udp_multicast $ iojs receive-specific-address.js
listening on a specific address
server got: Direct Hello! from 10.80.10.23:8000

The problem has been reproduced with io.js 1.6.4 and 2.0.1 (linux armv6l, linux x64).

[yosuke-furukawa]

Have you tried the multicast address 224.0.0.114 ??
I tried your scripts on the address, it works fine.

And according to our api docs, example code uses 224.0.0.114.
https://iojs.org/api/dgram.html

[tberthe]

I tried with 224.0.0.114 but have the same issue.
I checked the packets with Wireshark and can confirm that the membership is properly added and the multicast message is sent.

[Trott]

I get the same behavior as @tberthe whether I use 224.0.0.114 or 225.0.0.1 (after updating LOCAL_IP to be my IP), and I get that behavior whether I use Node.js 1.6.4 or Node.js 5.7.1.

[j8la]

I have exactly the same issue but only on Linux (Debian 8.4), use bind with a specific address is working fine on Windows (10). Linux sends packets with specific address but cannot receive. With Linux or Windows, i have multiple interfaces (ethernet, wifi, Docker...). I'm using Node 6.1.0. Tested with many multicast addresses without success. Disabling the unused interfaces has no effect.

[santigimeno]

I've been looking into this and think it works as expected. IIUIC, to receive a multicast datagram you have 2 options:

• binding only to the PORT the multicast message is sent and joining the multicast group i.e.: as in receive-all-addresses.js. This way, you can receive every message sent to that port whether multicast or not.
• binding to the PORT and the multicast address and joining the multicast group. This restricts the messages received to multicast only. As in receive-specific-address.js but binding to MULTICAST_IP instead of LOCAL_IP.

On the other hand, if you want to restrict from which interface the multicast messages are received you can use the multicastInterface argument in addMembership. For example: s.addMembership(MULTICAST_IP, LOCAL_IP); will allow to receive multicast messages received in the LOCAL_IP interface.

[j8la]

Thanks @santigimeno, works for me :-)

[santigimeno]

Closing this. If anyone feels it should be re-open, please do.