Task 2: TCP server

In this assignment, you will implement a TCP server that gets incoming connection requests and should send a number of bytes as requested by the client.

The course git repository contains Rust templates for this task that you may use if you want.

Follow these steps in your program:

1. Open a listening TCP socket that binds to a port of your choice. You should choose a port number between 1024 and 49151

2. Send a control message to the adnet-agent server that follows this form: TASK-002 keyword IP:port. As in the previous task, keyword is a random word you receive in the MyCourses assignment. IP is the IP address your program runs at listening to incoming connections, and port is the port that you chose to bind for listening. If you are running your program in node “lh1” of our simple_topo Mininet configuration, the IP address is 10.0.0.1.

3. adnet-agent starts opening connections to your server. There will be altogether three concurrent connections. A client first sends 5 bytes of data. The first four bytes are a 32-bit unsigned integer in network (big-endian) byte order. This tells how many bytes the agent expects to receive from this socket. You should send this many bytes, all containing the value indicated by the fifth byte in the request from adnet-agent. Note that your implementation should be prepared to handle multiple connections in parallel.

4. When you have finished sending the requested number of bytes, you should output the following to the terminal: “Wrote N bytes of byte B”. A new request may arrive from a client, with a similar 5-byte format, to which you should respond in the same way as described above. If a client does not need more data from this socket, it closes the TCP connection. Your program should therefore be able to handle closing a TCP connection without problems. Note that while one connection closes, there may be other connections still open, performing transmission.

5. When adnet-agent has closed all the connections it opened at the beginning, this assignment is complete and successful.

The diagram below illustrates the expected communication between your implementation and adnet-agent.

Execute your program and the adnet-agent in the Mininet simple_topo topology. As in the previous assignment, adnet-agent should run in host “rh1”, and your implementation should run in host “lh1”. Run your implementation in Mininet configuration with the following properties: sudo aalto/simple_topo.py --delay=50ms --bw=0.5. You can also try other scenarios if you are interested.

You should submit the output of your program to MyCourses, consisting of multiple lines of the above-mentioned “Wrote N bytes of byte B” messages.

Tips

• In Rust you can convert unsigned 32-bit integer (u32 type) into big-endian 4-byte array using the to_be_bytes function (example), and vice versa using the from_be_bytes function (example)

• See the different server examples for various design alternatives (non-blocking events, thread-based, collaborative multitasking). Which one would be most suitable in this case?