Python websocket context manager with while True in body, closing connection

Question

来自下一个测试代码

    async def hello():
    uri = "ws://localhost:8765"

    while True:
        async with websockets.connect(uri) as ws:
            await ws.send("Test \n")
            await asyncio.sleep(1)


if __name__ == "__main__":
    asyncio.run(hello())

此代码执行每秒发送一条消息的预期行为，但似乎通过进行如下所示的更改可以提高效率：

    async def hello():
    uri = "ws://localhost:8765"

    
    async with websockets.connect(uri) as ws:
        while True:
            await ws.send("Test \n")
            await asyncio.sleep(1)


if __name__ == "__main__":
    asyncio.run(hello())

但是，在第二种方法中，上下文管理器退出并输出下一个异常：

    raise self.connection_closed_exc()
    websockets.exceptions.ConnectionClosedOK: code = 1000 (OK), no reason

如果正文在上下文管理器中正确缩进，为什么上下文管理器会关闭连接？

Answer 1

您可能正在关注 websockets 图书馆 example。

如示例中所写：

On the server side, websockets executes the handler coroutine hello once for each WebSocket connection. It closes the connection when the handler coroutine returns.

下面是示例中的 Websockets 服务器：

import asyncio
import websockets

async def hello(websocket, path):
    name = await websocket.recv()
    print(f"< {name}")

    greeting = f"Hello {name}!"

    await websocket.send(greeting)
    print(f"> {greeting}")

start_server = websockets.serve(hello, "localhost", 8765)

asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()

并且 Websockets 客户端修改为使用 while True 循环：

import asyncio
import websockets

async def hello():
    uri = "ws://localhost:8765"
    async with websockets.connect(uri) as websocket:
        name = input("What's your name? ")

        while True:
            print(websocket.closed)
            await websocket.send("Test")
            await asyncio.sleep(1)

        print(f"> {name}")

        greeting = await websocket.recv()
        print(f"< {greeting}")


asyncio.get_event_loop().run_until_complete(hello())

运行服务器然后客户端提供以下输出：

在服务器中：

< Test
> Hello Test!

在客户端：

What's your name? hi
False
True
...
websockets.exceptions.ConnectionClosedOK: code = 1000 (OK), no reason

在您介绍的第一个案例中，代码会在每次循环迭代时创建 websocket 连接。而在第二个中，代码重用了在处理后由服务器关闭的连接，如文档所述。您可以通过检查 websocket.closed 字段看到 websocket 连接已关闭。

Python websocket context manager with while True in body, closing connection

Python websocket context manager with a while True in body, closing connection

python

websocket

python-asyncio