Abstract: A communication system (10) comprises at least two communication networks (20, 22) over which communications between physical devices (14) connected to the communication networks are to be carried out. The communication networks (20, 22) implement different protocols for messaging. A communication server (12) acts between the communication networks. Messages between the communication networks pass through the communication server. The communication server includes a knowledge base (286) storing protocol conversion information. The communication server (12) accesses the protocol conversion information in the knowledge base (286) upon receipt of a message and converts the protocol thereof to a protocol compatible with the communication network to which the message is being sent.