A plurality of users communicate in a plurality of real-time text conversations (e.g., “chat sessions”) in a client-server message processing environment using messages including a conversation index, a conversation-initiator ID and a list of message recipients. Each conversation is maintained at client terminals in an individual window. Dropping and controlled adding of conversation participants is attended by message updates to other participants. Alternative peer-to-peer message handling reduces the processing burden on servers while allowing clients to perform control and display functions. Voice or other non-text messages are also communicated using described techniques.