A communication system is provided that is capable of flexibly dealing with conversations among agents. An agent includes a software part which performs operations that represent the functions of a human ear and a mouth. In generating a conversation, an agent communication language, which is similar to a human conversation, is prepared and sent to a conversation part as a message packet. The conversation part then generates a plurality of conversation threads one for each unit of conversation and converse with a plurality of nodes in parallel and asynchronously. On the other hand, in another node which receives the message packet, a protocol manager receives the data (message packet) from a network and passes it to the conversation part. The conversation part understands the message packet and executes the content. In the preferred embodiment of this invention, the conversation part moves to other places along with a mobile agent.