OOP Python 网络套接字

Question

我想将 python websockets 包的功能封装到 class 中，代表一个传感器协调器。这样做的目的是允许我创建一个协调器对象，并且只让服务器在需要时持续存在。不幸的是，我无法在网上找到任何类似的例子，并且到目前为止一直在努力。

我的代码如下：

import asyncio
import json
import logging
import websockets

logging.basicConfig()


class Coordinator(object):

    def __init__(self, host='localhost', port=8080):
        self.host = host
        self.port = port

        self.running = False

        self.server = None
        self.sensors = set()

    def __enter__(self):
        self.server = websockets.serve((self.ws_handler, self.host, self.port))
        self.running = True

    def __exit__(self, exc_type, exc_val, exc_tb):
        # Gracefully stop serving
        self.running = False
        pass

    def sensors_event(self):
        return json.dumps({'type': 'sensors', 'count': len(self.sensors)})

    async def notify_sensors(self):
        if self.sensors:
            message = self.sensors_event()
            await asyncio.wait([user.send(message) for user in self.sensors])

    async def register(self, websocket):
        self.sensors.add(websocket)
        await self.notify_sensors()

    async def unregister(self, websocket):
        self.sensors.remove(websocket)
        await self.notify_sensors()

    async def ws_handler(self, websocket):
        try:
            await self.register(websocket)
            pass

        finally:
            await self.unregister(websocket)


if __name__ == '__main__':
    with Coordinator() as coordinator:
        pass

目前看来 websocket 服务器没有启动，因为它在 netstat 上不可见。

是否可以运行服务器在一个单独的（恶魔化的）线程中，由协调器对象持有？

谢谢

Answer 1

您的代码有两个问题。

你永远不会启动 asyncio 主循环，所以 asyncio 永远没有机会运行。换句话说，您需要在代码中的某处包含 loop.run_until_complete(x)。
start_server是一个协程，所以你必须等待它。

代码的固定版本（但未经测试）可能如下所示：

class Coordinator(object):
    def __init__(self, host='localhost', port=8080):
        self.host = host
        self.port = port

        self.running = False

        self.server = None
        self.sensors = set()

    async def __aenter__(self):
        self.server = await websockets.serve((self.ws_handler, self.host, self.port))
        self.running = True

    def __aexit__(self, exc_type, exc_val, exc_tb):
        # Gracefully stop serving
        self.running = False

    def sensors_event(self):
        return json.dumps({'type': 'sensors', 'count': len(self.sensors)})

    async def notify_sensors(self):
        if self.sensors:
            message = self.sensors_event()
            await asyncio.wait([user.send(message) for user in self.sensors])

    async def register(self, websocket):
        self.sensors.add(websocket)
        await self.notify_sensors()

    async def unregister(self, websocket):
        self.sensors.remove(websocket)
        await self.notify_sensors()

    async def ws_handler(self, websocket):
        try:
            await self.register(websocket)
        finally:
            await self.unregister(websocket)

async def main():
    async with Coordinator() as coordinator:
        pass


if __name__ == '__main__':
    asyncio.get_event_loop().run_until_complete(main())

如果您花时间了解 a tutorial 涵盖基本异步概念的内容，例如运行主循环，使用 asyncio 会容易得多。

Answer 2

来自high-level documentation:

The websockets.server module defines a simple WebSocket server API.

serve() returns an awaitable. Awaiting it yields an instance of WebSocketServer which provides close() and wait_closed() methods for terminating the server and cleaning up its resources.

On Python ≥ 3.5, serve() can also be used as an asynchronous context manager. In this case, the server is shut down when exiting the context.

正如@user4815162342 已经确定的那样，主要问题是您不等待对 serve() 协程的调用。

由于您使用的是 Python v3.6.8，因此您可以使用异步上下文管理器来简化实施。这样做的好处是您无需担心处理关机，因为它是自动处理的。这是一个简单的回显服务器的面向对象的实现。

import asyncio
import signal
import websockets

class Server(object):

    def __init__(self, host, port):
        self.host, self.port = host, port
        self.loop = asyncio.get_event_loop()

        self.stop = self.loop.create_future()
        self.loop.add_signal_handler(signal.SIGINT, self.stop.set_result, None)

        self.loop.run_until_complete(self.server())

    async def server(self):
        async with websockets.serve(self.ws_handler, self.host, self.port):
            await self.stop

    async def ws_handler(self, websocket, path):
        msg = await websocket.recv()
        print(f'Received: {msg}')

        await websocket.send(msg)
        print(f'Sending: {msg}')


if __name__ == '__main__':
    server = Server(host='localhost', port=6789)

目前，这将运行直到用户发送中断，但您可以调整 stop 未来以适应。

OOP Python 网络套接字

OOP Python websockets

python

websocket

python-asyncio

macos-mojave