7.1 Communication protocol - Overview

Applications will communicate with each other by participating in the same session. The session will consist of one or more Virtual Connections. Virtual Connection will link application with Central Server. Virtual Connection will consist of connection between Application and Demon and Demon and Central Server. The connections will be implemented as Internet socket connections (The only exceptions are Java Applets communicating Demon by the use of method invocation). Demon to Central Server connection will use TCP stream. Application will have possibility of communicating with demon using either UDP packets or TCP streams.

When Application is started by the the Demon it obtain a port number to communicate with. On server side the application will be assigned unique application id number (AID). This number will be known to the Demon which will maintain a table translating AID to communication port numbers. Information comming from the Server is resent to appropriate Applications.

Server identifies the user by the communication link it uses to contact the Server. Then the appropriate session for this particular application is found, and message is resent to the Demons of all other session participants.