Client-Server Model

The server basically sleeps, waiting to be contacted by clients. There are 2 kinds of servers:

• [Iterative:] for short jobs. E.g., serve time of day.
• [Concurrent:] for long services. It typically uses the UNIX fork and perhaps exec system calls.

SERVER PROGRAM:

1. Open communication channel and inform local host that it is waiting at some (well-known) port.
2. Waits for clients.
3. Serves clients (perhaps after forking)
4. Goes back to waiting.

CLIENT PROGRAM:

1. Open communication channel and connects to a server port.
2. Sends request to server.
3. Receives response.
4. Close channel.