Implement Length-Prefixed Message Framing - The Networker

                      TASK
                    

Implementation

TCP is a byte stream, not a message protocol. You need framing to know where one message ends and the next begins. Length-prefixed framing prepends each message with its size.

Format: [4-byte big-endian length][payload]

Implement send_frame and recv_frame:

Request:  {"type": "frame_encode", "msg_id": 1, "payload": "hello world"}
Response: {"type": "frame_encode_ok", "in_reply_to": 1, "frame_hex": "0000000b68656c6c6f20776f726c64", "total_bytes": 15}

Request:  {"type": "frame_decode", "msg_id": 2, "frame_hex": "0000000b68656c6c6f20776f726c64"}
Response: {"type": "frame_decode_ok", "in_reply_to": 2, "payload": "hello world", "payload_length": 11}

Request:  {"type": "frame_decode_partial", "msg_id": 3, "chunks": ["0000000b68", "656c6c6f20", "776f726c64"]}
Response: {"type": "frame_decode_partial_ok", "in_reply_to": 3, "payload": "hello world", "chunks_needed": 3}

Sample Test Cases

Encode a simple messageTimeout: 5000ms

Input

{"src":"c0","dest":"n1","body":{"type":"init","msg_id":1,"node_id":"n1","node_ids":["n1"]}}
{"src":"c1","dest":"n1","body":{"type":"frame_encode","msg_id":2,"payload":"hello"}}

Expected Output

{"src": "n1", "dest": "c0", "body": {"type": "init_ok", "in_reply_to": 1, "msg_id": 0}}
{"src": "n1", "dest": "c1", "body": {"type": "frame_encode_ok", "in_reply_to": 2, "frame_hex": "0000000568656c6c6f", "total_bytes": 9, "msg_id": 1}}

Decode a framed messageTimeout: 5000ms

Input

{"src":"c0","dest":"n1","body":{"type":"init","msg_id":1,"node_id":"n1","node_ids":["n1"]}}
{"src":"c1","dest":"n1","body":{"type":"frame_decode","msg_id":2,"frame_hex":"0000000568656c6c6f"}}

Expected Output

{"src": "n1", "dest": "c0", "body": {"type": "init_ok", "in_reply_to": 1, "msg_id": 0}}
{"src": "n1", "dest": "c1", "body": {"type": "frame_decode_ok", "in_reply_to": 2, "payload": "hello", "payload_length": 5, "msg_id": 1}}

Hints

Hint 1▾

Each message is [4-byte big-endian length][payload]

Hint 2▾

The receiver must read exactly 4 bytes first to get the length

Hint 3▾

Then read exactly length bytes for the payload

Hint 4▾

TCP does not guarantee message boundaries; handle partial reads

Hint 5▾

Use a buffer to accumulate bytes until a full frame is available

Resources

Message Framing in TCP

Comprehensive overview of different message framing strategies for TCP

                      OVERVIEW
                    

Theoretical Hub

Concept overview coming soon

Key Concepts

message framinglength prefixTCP streampartial reads

main.py

python