Program 4


Typically, the server in a client-server relationship has to be able to handle multiple clients. An FTP, Telnet, mail, file or name server wouldn't be of use if you had to take turns with a legion of unknown competing users. This problem is handled by having the server create a child process to handle each client. This is described in more detail in the Unix Network Programming Manual .

For this assignment, your are going to create a server to handle multiple clients as described in the lab. Every new client will get a child process sub-server that actually communicates with the client.

This is easiest done by building a server to handle a single client, making sure that the part that handles the client is isolated from everything else. Then expand it to a multiple client structure. It is vital that you properly terminate the child processes, and that requires that the child exit AND THAT THE PARENT PERFORM A WAIT SO THAT THE CHILD PROCESS IS COMPLETELY REMOVED. This is described in the Unix Network Programming Manual, but is often overlooked by beginners.

The server you create is going to do what Program 3 did in providing clients with a random number fetch capability. There are no special modifications needed for this type of service to multiple clients, since each is completely independent of the other. This will not always be the case.

When creating your server, have it output data on every new client connection, reporting the address of the client and the port being used. The getsockname call applied to the socket returned by the accept statement can be used to get this information.

Get this part going before attempting Part B.

Part B

The second part of this assignment requires that you set up pipes between the server and the sub-server with the server generating all of the random numbers and the sub-servers communicating their needs. So you need a pair of pipes for each sub-server. The sub-server will send a message to the server when it needs a random number on one pipe, and receive the random number on the other pipe. You might be thinking that this is simple busy-work, but this is typically what you would do. When generating random numbers, you want to have one generator to avoid bias.

Run your server and at least three clients. Turn in a script of the output from the clients and servers along with the source code.