By default, the connectionless User Datagram Protocol (UDP) is used to send Communicator Heartbeat from managed product to the Control Manager server.
Making incorrect changes to the configuration file can cause serious system problem. Back up TMI.cfg to restore your original settings.
Set all TMI.cfg in your Control Manager network (server and agents) to the same security level value (AllowUDP). Otherwise, the server and agent communication will not work.