I'm not 100% clear on what you want but I've got a thought that might work. If the broadcast includes the senders address, then the recieving server could initiate a TCP connection to the broadcaster in response. The sender would then only accept the first connection and refuse the others so that if multiple servers replied you would just deny their connections.

I'm picturing 1 computer deciding it needs job A done. So it broadcasts out saying it needs a type A server. Each type A server then replys with a TCP connection. Each type A server could have a built in delay before replying, so the primary would reply immediatly and backups a random number of seconds later. In this way the client just accepts the first connection and proceeds with its needs.