[Bug]: _recv_line() can block on partial TCP receive #1

New Issue

2026-04-17T11:27:59Z

tgohle commented

2026-04-17 11:27:59 +00:00

Problem

_recv_line() can block indefinitely if the newline does not arrive at the end of a single recv() chunk.

Current code

def _recv_line(self) -> str:
    chunks = []
    while True:
        b = self.sock.recv(4096)
        if not b:
            break
        chunks.append(b)
        if b.endswith(b"\n"):
            break

Why this is a bug

recv(4096) can return partial TCP chunks.

If the instrument sends OK\n but it arrives as two calls such as OK + \n, the b.endswith(b"\n") check on the first chunk misses the line ending. That can leave the function waiting longer than expected or blocking until timeout or socket close.

Fix approach

Accumulate into a bytearray and check the joined buffer for b"\n" instead of only checking the most recent chunk.

Status

Local fix already implemented in the current v0.2 working copy.
Still needs commit, push, and hardware verification before closing.

### Problem `_recv_line()` can block indefinitely if the newline does not arrive at the end of a single `recv()` chunk. ### Current code ```python def _recv_line(self) -> str: chunks = [] while True: b = self.sock.recv(4096) if not b: break chunks.append(b) if b.endswith(b"\n"): break ``` ### Why this is a bug `recv(4096)` can return partial TCP chunks. If the instrument sends `OK\n` but it arrives as two calls such as `OK` + `\n`, the `b.endswith(b"\n")` check on the first chunk misses the line ending. That can leave the function waiting longer than expected or blocking until timeout or socket close. ### Fix approach Accumulate into a `bytearray` and check the joined buffer for `b"\n"` instead of only checking the most recent chunk. ### Status Local fix already implemented in the current v0.2 working copy. Still needs commit, push, and hardware verification before closing.

tgohle added the

labels 2026-04-17 11:37:34 +00:00