Task: Ordered Client-Server Communication

Navigate to labs/lab-11/tasks/client-server/ and run make to generate the support directory. This exercise will guide you in creating a basic messaging protocol between a server and a client. Although in real-world applications a server typically handles multiple connections at once, here we focus on a single connection. Handling multiple connections is further explored in I/O multiplexing.

Our application protocol is defined as follows:

  • The server listens for connections on localhost and a specified port.
  • The client connects to localhost:port.
  • The client sends a message, which the server then prints, responds to, and the client prints the reply. This sequence repeats in a loop.
  • The communication ends when either the client or the server sends the message exit.

Since we are blocking on recv(), the message order is fixed - the client must initiate communication. In real-world applications, this constraint can be avoided with I/O multiplexing.

  1. Open support/client.c and complete the TODOs to enable message exchange with the server. Test your client by running python server.py in one terminal and then ./client in another. If correctly implemented, you should be able to exchange messages as outlined above.

    Bonus Question: Why is it OK for the client to be implemented in C while the server is implemented in Python?

  2. Open support/server.c and complete the TODOs to enable message exchange with the client. Test your server by running ./server in one terminal and then python client.py in another. If implemented correctly, you should be able to exchange messages as outlined above.

If you’re having difficulties solving this exercise, go through the sockets API and the client-server model.