Python websockets lib 客户端持久连接(带类实现) [英] Python websockets lib client persistent connection (with class implementation)

问题描述

我正在尝试使用 websockets 和我以前从未使用过的明显强制性的 asyncio 在 python 中实现一个 websocket 客户端(我很难理解...).

I'm trying to implement a websocket client in python using websockets and the apparently mandatory asyncio which I never used before (and I have a hard time to understand...).

我已经阅读了很多关于这个主题的文章，并且在这里和到处都看到了(太多)很多例子，但我找不到一种方法来正确地制作一个具有持久连接的 websocket 客户端.

I've read a lot on the subject and saw (too) many examples here and everywhere, but I can't find a way to properly make a websocket client with a persistent connection.

• 我需要一个持久连接，因为需要在同一个连接上请求命令，第一个是身份验证命令.
• 远程服务器是我无法控制的第 3 方 API.
• 我想我可以在程序发送的每个命令的同时运行一个身份验证请求，但是对于每个命令打开 > auth > request > close 而不是在整个程序的生命周期中保持一个连接处于活动状态，这感觉不对
• 我的实现是一个使用许多类的库，我需要将 websocket 连接器/处理程序包装在其中一个中

以下是我现在所拥有的，基于我在这里和那里找到的示例(带有一些混淆数据):

Here's what I have right now, based on examples I found here and there (with some obfuscated data) :

import json
import asyncio
from websockets import connect


URL = 'wss://server.com/endpoint'


class Websocket:
    async def __aenter__(self):
        self._conn = connect(URL)
        self.websocket = await self._conn.__aenter__()
        return self

    async def __aexit__(self, *args, **kwargs):
        await self._conn.__aexit__(*args, **kwargs)

    async def send(self, message):
        await self.websocket.send(message)

    async def receive(self):
        return await self.websocket.recv()


class Handler:
    def __init__(self):
        self.wws = Websocket()
        self.loop = asyncio.get_event_loop()

    def command(self, cmd):
        return self.loop.run_until_complete(self.__async__command(cmd))

    async def __async__command(self, cmd):
        async with self.wws as echo:
            await echo.send(json.dumps(cmd))
            return await echo.receive()


def main():
    handler = Handler()

    foo = handler.command('authentication command')
    print('auth: ', foo)

    bar = handler.command('another command to run depending on the first authentication')
    print('command: ', bar)


if __name__ == '__main__':
    main()

基本上现在我得到这些答案(简化和混淆):

Basically right now I get these answers (simplified and obfuscated) :

auth: Ok, authenticated
command: Command refused, not authenticated

我想我的问题是块 async with self.wws as echo: 有点创建连接，运行它的代码然后删除它而不是保持连接活动.由于我们在这里没有使用通常的 __init__ 而是一些 asyncio 巫术，我不明白，我有点卡住了.

I suppose my problem is that the block async with self.wws as echo: kind of create the connection, runs its code then drop it instead of keeping the connection alive. Since we are not using a usual __init__ here but some asyncio voodoo I don't understand, I'm kind of stuck.

推荐答案

我认为你的诊断是正确的，问题是异步上下文管理器为 Handler.command 的每次调用创建和关闭连接代码> ...真的不想要你想要的.

I think your diagnosis is correct, the problem is that the async context manager it creating and closing a connection for each call of Handler.command ... really not want you want.

相反，您可以在 Handler 初始化期间同步建立 websocket 连接，然后将连接 websocket(类型为 WebSocketClientProtocol 的实例)存储为类成员以备后用，如本示例代码所示:

Instead you could just synchronously establish the websocket connection during the init of Handler and then store the connection websocket (instance of type WebSocketClientProtocol) as a class member for later use, as in this sample code:

import json
import asyncio
from websockets import connect

URL = 'ws://localhost:8000'

class Handler:

    def __init__(self):
        self.ws = None
        self.loop = asyncio.get_event_loop()
        # perform a synchronous connect
        self.loop.run_until_complete(self.__async__connect())

    async def __async__connect(self):
        print("attempting connection to {}".format(URL))
        # perform async connect, and store the connected WebSocketClientProtocol
        # object, for later reuse for send & recv
        self.ws = await connect(URL)
        print("connected")

    def command(self, cmd):
        return self.loop.run_until_complete(self.__async__command(cmd))

    async def __async__command(self, cmd):
        await self.ws.send(json.dumps(cmd))
        return await self.ws.recv()


def main():
    handler = Handler()

    foo = handler.command('authentication command')
    print('auth: ', foo)

    bar = handler.command('another command to run depending on the first authentication')
    print('command: ', bar)


if __name__ == '__main__':
    main()

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