Due date

Submission medium

Group work

Assignment

1. One HTML file index.html. The document discusses your design and implementation and gives some examples of use. The file should only refer to files in the same directory. Also document your code lavishly !
2. One Makefile. Typing "make" should build the executables.
3. One services.h to be included in various places which lists symbolic names for the services (SUM and PRODUCT).
4. Once net_client.c. The net_client.c provides services to access the network, namely access remote procedures. The user must be able to link a client.c application with net_client.c to access functions int plus(int, int) and int product(int, int) on a server as if they were local. To find out which server (IP address and port number) provides plus() and product(), the client will contact the dispatcher. If the connection to the dispatcher fails, the client retries upto MAX_RETRIES times after a certain delay time. The delay time is initially RETRY_DELAY. Upon each retry, the delay is doubled. If the connection to the server fails, the client exits. A more realistic application would contact the dispatcher again.
5. Once net_server.c. The net_server.c provides (remote) procedure/function services to connecting clients. The user must be able to link a server.c application with net_server.c to provide the actual function implementations int plus(int, int) and int product(int, int). Both functions will call sleep(DELAY) to emulate major computation (DELAY=30s). A server will announce its availability as well as services it offers and on which IP address/port to the dispatcher. Once it has finished doing so, it will listen to the advertised IP address/port to service client calls. The server should handle the SIGINT interrupt gracefully: before terminating, it must warn the dispatcher it is no longer available. The server must be implemented as a concurrent server.
6. One dispatch.c (iterative server) which accepts connections from clients as well as from servers. The server will announce its availability as well as services it offers and on which IP address/port. This information will be stored in a table in the dispatcher. A lookup in this table will be perfomed to answer a client query (which server can process its requrest). Come up with a "reasonably fair" way of performing the lookup (such as round-robin).

Some remarks:

• As client and server machines may use a different byte order, care must be taken when transmitting function arguments.
• The IP address and port number of the dispatcher should be command line arguments (use getopt() for example) for clients and servers. Optionally, they may be #define'd in the source code.
• Use TCP/IP (not UDP).
• The dispatcher may receive messages from both clients and servers. Either the dispatcher listens (I/O multiplexing with select()) to multiple ports or it listens to a single port. In the latter (simplest implementation) case, the message must contain a code indicating the message type (from client or from server). Note how in this case, using select() is overkill, so you are advised to use a code.
• Client, dispatcher, server should all do verbose logging of their activities to stderr.
• The above specification does not go into detail which leaves many options open. Use common sense and document your design/implementation decisions !
• Implement 3 prototypes: client-iterative server only, client-concurrent server only, client-dispatcher-concurrent server. Partial marks will be given for working prototypes. If your full solution works, there is no need to submit more than that. The prototypes will help you tackle the complexity and allow for partial marks.

Resources

Check the Class Transparencies page to find more information about TCP/IP.