Question

I am looking into UDP multicast for host discovery on a LAN.

I have it working well with hosts on separate computers. When a peer first run they subscribe to the group, send a simple announcing message consisting of their userID and online, they then listen to the group for other peers announcing their arrival in the same fashion.

Whilst a peer can identify other peers subscribing to the group “after” they have arrived. They do not see who subscribed to the group “before” they did.

My question, is it possible for a host to get a list of all the other hosts subscribing to the same group they are?

My aim is for each peer (host) subscribing to the group to have a dropdown list of the userID’s of all other peers (hosts) currently subscribing to the group.

Thanks,

Answer 1

No, there is no central authority of group membership. You have two choices:

1. Set up a master/slave protocol that allows the peers to elect a master to which new peers can send group membership queries (a la NetBIOS)
2. Have each peer send its own membership announcement message periodically so new members can eventually accumulate a list of peers.