Thanks,I don't know the topic you reply,I will see it.

In my opinion, I think I can send pong message to clients in LAN,so they can gain my address,but If I multicast the pong messages,the different udp port the Lan clients bind will be a problem,do you know how to solve the problem?

Why I choose multicast ，because I don't the clients address in LAN，but I want to notice them，so how do you think of this？

Is there some better implementation to solve it?