Difficulty with UDP Socket Data Fragmentation and Reassembly in Python 3.11
I'm a bit lost with I tried several approaches but none seem to work. I'm working on a UDP socket application in Python 3.11 where I need to send large payloads of data. I am working with issues with data fragmentation when the payload exceeds the maximum transmission unit (MTU) size. I attempted to break the large messages into smaller segments, but the reassembly on the receiving end seems to be failing, leading to incomplete data. Here's a simplified version of my sending code: ```python import socket def send_large_message(message, address): sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) MAX_MESSAGE_SIZE = 1400 # Just below typical MTU segments = [message[i:i + MAX_MESSAGE_SIZE] for i in range(0, len(message), MAX_MESSAGE_SIZE)] for segment in segments: sock.sendto(segment.encode(), address) sock.close() ``` On the receiving side, I'm trying to collect the incoming segments like this: ```python import socket def receive_messages(port): sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.bind(('', port)) full_message = '' while True: data, addr = sock.recvfrom(1500) full_message += data.decode() if not data: break # Assuming empty message indicates end sock.close() return full_message ``` I am observing that the full_message ends up being incomplete, and I suspect that this is due to the way I'm determining when to stop receiving. I also noticed that the order of segments might not be preserved as UDP doesn't guarantee it. Here are a couple of the behavior messages I've encountered: `IndexError: string index out of range` when accessing segments in the sending function, and `UnicodeDecodeError` when the reassembled message contains unexpected byte sequences. I've tried adjusting the MTU size and using different buffer sizes in the receiving function, but I still face issues. Any pointers on best practices for handling UDP message segmentation and reassembly would be appreciated. Am I missing something fundamental in my approach? My development environment is Ubuntu 22.04.