VC Communication Server

Figure 1: VC System Diagram

How does VC System work?

Step1: When client tools (Teacher or Student Client) start up, they will first authenticate   with Name Server. If pass, the name server will provide the address and port of VC server according to the course users selected.

Step2: The following communication is between the clients and the VC server. No direct communication among clients. The VC server maintains a list of all active clients, and broadcasts all the incoming message sent by clients. 

Step3: When a client exits, a message will be sent to VC server. The server will relay this message as well as others. So all other clients will know that he/she left.

Note: There must be a single Name Sever in the VC system, however, there could be multiple VC servers (for different courses).

Working Procedure of VC Server

Procedure VCServerStart() {

Register Address/Port with Name Server;

While (Listen for incoming message) {

Switch (Message.Type)

// the client just passed authentication

Case Login Message:

   Add Client Name into list;

   Generate signature for the client;

   send the signature back to client;

   //for updating Visual Classroom;

   send the active user list to client;

   break;

Case Other Messages:

   check the signature of message;

   lookup client name by the signature;

   Add name into the messages;

   broadcast the message to all clients;

   break;

}//end of while

}//end of procedure

Updated: 10/17/2005