Client-Server programming using TCP\IP



Description of the program:

The program implements the prototype of client-dispatcher-concurrent server using TCP/IP.

The dispatcher is implented as an iterative server, which serves both servers and clients. It listens to a single port. It receives information from a server after the server is set up and stores the sever information into corresponding list accord ing to the service the server offers. It will delete the server information after it received the exit information from that server. It receives client request for some specific service. If the service is available at some server, the dispatcher then send s the information of that server to that client. The server pickup is in Round-Robin rotation.

A server is implemented as a concurrent server. When it is set up, it first sends its information (IP address, port number and service available on this server) to dispatcher. After that, it listens at its well-known port to serve the client servic e request. When a client service request is accepted, the server will fork a child server to serve this client. The server itself will keep listening on its well-known port. After the child server finished its job, it will exit. The parent server then han dles SIGCHLD, avoiding zombie process.

A client first contacts the dispatcher. If the connection to the dispathcer fails, the client retries upto 15 times after a certain delay time. The delay time is initially 30 seconds. Upon each retry, the delay is doubled. If the connection to disp atcher is established, the client will send its service request to the dispatcher, and the client will get some information back from the dispatcher. If the service is available on some server, the information is the IP address and port number of that ser ver; if the service is not available, the client will retry to contact the dispatcher for 15 times after certain delay time. After having the information of the sever, the client will contact the server to access the remote procedure. If the connection to server fails, the client will exit.

How to compile the program?

prompt>make

How to execute the program?

1.Set up the dispatcher on willy, nova or mimi. The dispatcher will alway listen on the port 3498.

prompt>dispatcher

2.Set up servers on willy, nova or mimi. There can be only one server on each machine. The well-known port is 9003.

prompt>server 132.206.51.205 3498

The comand line parameters are the IP address of the dispatcher(depends on which machine it stays on) and the well-known port number of the dispatcher 3498.

3.Set up clients on willy, nova or mimi. There can be any number of clients on each machine.

prompt>client 132.206.51.205 3498

The comand line parameters are the same as the server's.

Note: The setup may not follow the above order. If then, the client will not be served until the dispatcher and the server, which has the service the client needs, are set up. Some corresponding message will be given to the client.


Example of Execution

All files included:

  • dispatcher.c:
       The source code for the dispatcher.
  • server.c:
       The source code for the server
  • client.c:
       The source code for the client
  • net_client.c:
       The source code that contains serveral functions to be used by clients.
       It is linked with client.c.
  • net_server.c:
       The source code that contains functions to be used by servers.
       It is linked with server.c.
  • common.c:
       The source code that contains server functions to be used by dispatcher,client,and server.
       It is linked with client.c,dispatcher.c and server.c.
  • service.h:
       The header file that contains #defines ,#includes and prototypes of functions.
  • makefile:
       The make file