ListenForClients is getting invoked twice (on two different threads) – once from the constructor, once from the explicit method call in Main. When two instances of the TcpListener try to listen on the same port, you get that error.
ListenForClients is getting invoked twice (on two different threads) – once from the constructor, once from the explicit method call in Main. When two instances of the TcpListener try to listen on the same port, you get that error.