1. Client/Server Socket Programming Project
D-A Dick
D-A Eddy
D-A Ricky

2. Concurrent connection-oriented server
Topic Simple ICQ program
Communication between client and server (TCP) The server create socket and bind, the server will go to listen state, when client connect to server, if the server accept it, fork the slave process to serve the client, the client send request and slave process will respond to client

3. Communication between client and server (TCP)

4. Communication between client and client (UDP)
Client A want to send message to client B
Client A will send request of find address client B to server
Client A received address of client B address from the server
Then client can user UDP socket to send message to client B
Client B received message

5. System Design Server side windows display client’s IP and port number,
“flag” to identify which process
when the server need to respond to client
it also display the system message

6. System Design cont’ Client side window
Client command window Communicate with server, choose operation and display
system message, such as login successful
Received message window
Display message from other client
Show the ID and IP who user send message

7. System Design cont’ the Server Side
The server only have TCP connection with user, the server is sitting at the MYPORT to waiting client request
When the client login to server, the server will verify the client information such as user id, pwd
All the client information will save at “list.dat” file,

8. System Design cont’ The file “list.dat” using structure
The client record struct record { int id; /* user id */ int pws /* user password */ char ip[15]; /* save the client ip */ int port; /* save the client receiving port */ };

9. System Design cont’
When the client A want to send the message to client B the client A first to use TCP socket to communicate to server request the client B address IP and port
Then the server will fetch the client B address and sent to client A, after the client A receive that message, then he can the UDP socket to send the message

10. Defined application protocol
One protocol between the client and server TCP socket communication: structure icq struct icq {
int flag; /* identify which function client request */ int id; /* user id * / int pwd; /* user password */ int port; /* user port */ char ip[15]; /* user IP address */ }

11. Defined application Protocol
Another protocol between client and client UDP socket communication: structure msg; struct msg { int id; char message[MAXDATASIZE]; };
Variable statement ID – this ID number is the send message client user ID Message – the char array contain message