Task: Async Server

Navigate to labs/lab-11/tasks/async-server and run make to generate the support files. Enter support and run make test-file.txt to generate the test file.

This task builds on the previous example of a multiplexed client-server. The server accepts connections from clients and downloads a file of 1 GB from each. After uploading the file, the clients close the connection.

1. Open server.c and complete the TODOs in the main function to setup IO multiplexing using epoll. Use epoll_create(), epoll_wait(), and the wrappers defined in w_epoll.h to handle descriptors without blocking. Remember to remove the client sockets from the epoll instance before closing them.

   To test, run ./server in one terminal and ./client in another terminal.s If successful, the clients should print the upload progress.

2. There is a problem with our current implementation. Try to start two clients at the same time - the first one will start uploading, and the second one will block at connect(). This happens because, even though we are multiplexing file descriptors on the server-side, it is busy with another client. To account for this, complete the TODOs in handle_client() to serve each client on a different process.

   To test, start python server.py in one terminal and run your client implementation in two separate terminals. If successful, the clients should be able to upload at the same time.

If you’re having difficulties solving this exercise, go through Async I/O and I/O Multiplexing.