为啥当客户端断开连接时这个简单的 websocket 代码会抛出？

Posted 2023-02-16

【中文标题】为啥当客户端断开连接时这个简单的 websocket 代码会抛出？

【英文标题】：Why does this simple websocket code throw when the client disconnects?为什么当客户端断开连接时这个简单的 websocket 代码会抛出？

【发布时间】：2018-10-07 09:59:40

【问题描述】：

我正在编写一些基于these docs 的简单网络套接字代码。服务器应侦听网络套接字并仅使用 pong 响应 ping 消息。

我在 Python3 上运行，服务器代码如下所示：

import asyncio
import websockets
from jsonrpcserver.aio import methods
from jsonrpcserver.response import NotificationResponse

@methods.add
async def ping():
    return 'pong'

async def accept_connection(websocket, path):
    async for request in websocket:
        response = await methods.dispatch(request)
        if not response.is_notification:
            await websocket.send(str(response))

start_server = websockets.serve(accept_connection, 'localhost', 5000)
asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()

客户端在 Dart 中，只需调用两次 ping 然后关闭连接。当客户端断开连接时，服务器的输出会出现此错误：

Dannys-MacBook:pythonws danny$ python3 server.py 
--> "jsonrpc":"2.0","method":"ping","id":0
<-- "jsonrpc": "2.0", "result": "pong", "id": 0
--> "jsonrpc":"2.0","method":"ping","id":1
<-- "jsonrpc": "2.0", "result": "pong", "id": 1
Error in connection handler
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/websockets/server.py", line 152, in handler
    yield from self.ws_handler(self, path)
  File "server.py", line 11, in accept_connection
    async for request in websocket:
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/websockets/py36/protocol.py", line 15, in __aiter__
    yield await self.recv()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/websockets/protocol.py", line 350, in recv
    yield from self.ensure_open()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/websockets/protocol.py", line 512, in ensure_open
    self.close_code, self.close_reason) from self.transfer_data_exc
websockets.exceptions.ConnectionClosed: WebSocket connection is closed: code = 1005 (no status code [internal]), no reason

根据上面链接的文档：

当客户端断开连接时迭代终止。

这让我相信它应该退出 async for 循环而不是抛出？

【参考方案1】：

https://www.pydoc.io/pypi/websockets-6.0/autoapi/protocol/index.html

迭代器产生传入消息。当连接关闭且状态码为 1000（OK）或 1001（正在消失）时，它会正常退出。当连接以任何其他状态码关闭时，它会引发 ConnectionClosed 异常。

从客户端以 1000 状态关闭可防止异常。