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On ESP32, after receiving 5-10 full websocket frames, this read returns only a partial frame:
payload = await self.reader.read(length) This is to be expected, as the read(length) call in MicroPython's asyncio.Stream is not guaranteed to return the full length bytes in a single call, especially for large payloads, due to non-blocking I/O or buffer constraints.
I didn't observe this issue on unix/desktop MicroPython, only on the ESP32.
The proper way is to re-do the read() for the remaining length until the entire frame has been received.
The patch below fixes that, as well as adding some error handling.
--- old/aiohttp_ws.py 2025-05-20 14:06:16.111521205 +0200 +++ aiohttp/aiohttp_ws.py 2025-05-20 14:16:28.985286423 +0200 @@ -197,13 +199,31 @@ return opcode, payload fin, opcode, has_mask, length = self._parse_frame_header(header) if length == 126: # Magic number, length header is 2 bytes - (length,) = struct.unpack("!H", await self.reader.read(2)) + length_data = await self.reader.read(2) + if len(length_data) != 2: + print("WARNING: aiohttp_ws.py failed to read 2-byte length, closing") + return self.CLOSE, b"" + (length,) = struct.unpack("!H", length_data) elif length == 127: # Magic number, length header is 8 bytes - (length,) = struct.unpack("!Q", await self.reader.read(8)) - + length_data = await self.reader.read(8) + if len(length_data) != 8: + print("WARNING: aiohttp_ws.py failed to read 8-byte length, closing") + return self.CLOSE, b"" + (length,) = struct.unpack("!Q", length_data) if has_mask: # pragma: no cover mask = await self.reader.read(4) - payload = await self.reader.read(length) + if len(mask) != 4: + print("WARNING: aiohttp_ws.py failed to read mask, closing") + return self.CLOSE, b"" + payload = b"" + remaining_length = length + while remaining_length > 0: + chunk = await self.reader.read(remaining_length) + if not chunk: # Connection closed or error + print(f"WARNING: aiohttp_ws.py connection closed while reading payload, got {len(payload)}/{length} bytes, closing") + return self.CLOSE, b"" + payload += chunk + remaining_length -= len(chunk) if has_mask: # pragma: no cover payload = bytes(x ^ mask[i % 4] for i, x in enumerate(payload)) return opcode, payload Metadata
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