Potential issue joining multicast group?

[rwarner]

Currently debugging an issue potentially with this implementation of SSDP in Golang.

On my current machine, I have no issues with the Minidlna C implementation joining the 239.255.255.250:1900 socket and receiving multicast broadcasts from across subnets.

However, with the same exact interface and calling on this Server in Golang, I only get results for 0.0.0.0:1900 and do not have success with accessing this server like the 239.255.255.250:1900 socket Minidlna has.

Just to be clear, whenever this is ran I only ever get

sudo netstat -tulnp | grep 1900
udp 0 0 0.0.0.0:1900 0.0.0.0:*

Looking here:

dms/ssdp/ssdp.go

Lines 95 to 108 in 07c3224

	func makeConn(ifi net.Interface) (ret *net.UDPConn, err error) {
	ret, err = net.ListenMulticastUDP("udp", &ifi, NetAddr)
	if err != nil {
	return
	}
	p := ipv4.NewPacketConn(ret)
	if err := p.SetMulticastTTL(2); err != nil {
	log.Print(err)
	}
	// if err := p.SetMulticastLoopback(true); err != nil {
	// log.Println(err)
	// }
	return
	}

Is there any reason there isn't a JoinGroup used?

e.g.

// Bind the multicast group to the interface
if err := p.JoinGroup(&iface, groupAddr); err != nil {
    logger.Debugf("Failed to join multicast group: %v", err)
    return err
}

I haven't had a chance to try to compile a change myself with this repo and then re-implement the library in the other application but wanted to see if there was any decision made with the implementation for this as I haven't been having success as is.

Thanks

[anacrolix]

I think I wrote and tested this part in 2012 or so. I'm definitely open to improvements if they fix things for you! Thanks

[rwarner]

No problem sounds good. Looking at the commits I figured this might be the case. Will poke around, thanks!