Python 使用 asyncio 的简单套接字 client/server

Question

我想使用 asyncio 协程而不是多线程重新实现我的代码。

server.py

def handle_client(client):
    request = None
    while request != 'quit':
        request = client.recv(255).decode('utf8')
        response = cmd.run(request)
        client.send(response.encode('utf8'))
    client.close()

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('localhost', 15555))
server.listen(8)

try:
    while True:
        client, _ = server.accept()
        threading.Thread(target=handle_client, args=(client,)).start()
except KeyboardInterrupt:
    server.close()

client.py

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.connect(('localhost', 15555))
request = None

try:
    while request != 'quit':
        request = input('>> ')
        if request:
            server.send(request.encode('utf8'))
            response = server.recv(255).decode('utf8')
            print(response)
except KeyboardInterrupt:
    server.close()

我知道有一些合适的异步网络库可以做到这一点。但我只想在这种情况下只使用 asyncio 核心库，以便更好地理解它。

如果只在处理客户端定义之前添加 async 关键字就好了...这里有一段代码似乎可以工作，但我仍然对实现感到困惑。

asyncio_server.py

def handle_client(client):
    request = None
    while request != 'quit':
        request = client.recv(255).decode('utf8')
        response = cmd.run(request)
        client.send(response.encode('utf8'))
    client.close()

def run_server(server):
    client, _ = server.accept()
    handle_client(client)

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('localhost', 15555))
server.listen(8)

loop = asyncio.get_event_loop()
asyncio.async(run_server(server))
try:
    loop.run_forever()
except KeyboardInterrupt:
    server.close()

如何以最佳方式调整它并使用异步等待关键字。

Answer 1

最接近线程代码的字面翻译会像以前一样创建套接字，使其成为非阻塞的，并使用asyncio low-level socket operations 来实现服务器。这是一个示例，坚持更相关的服务器部分（客户端是单线程的并且可能很好）：

import asyncio, socket

async def handle_client(client):
    loop = asyncio.get_event_loop()
    request = None
    while request != 'quit':
        request = (await loop.sock_recv(client, 255)).decode('utf8')
        response = str(eval(request)) + '\n'
        await loop.sock_sendall(client, response.encode('utf8'))
    client.close()

async def run_server():
    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server.bind(('localhost', 15555))
    server.listen(8)
    server.setblocking(False)

    loop = asyncio.get_event_loop()

    while True:
        client, _ = await loop.sock_accept(server)
        loop.create_task(handle_client(client))

asyncio.run(run_server())

以上方法有效，但不是 asyncio 的预期使用方式。它非常低级，因此容易出错，需要您记住在套接字上设置适当的标志。此外，没有缓冲，因此像从客户端读取一行这样简单的事情变成了一件令人厌烦的苦差事。这个 API 级别实际上仅适用于替代事件循环的实现者，它将提供 他们的 sock_recv、sock_sendall 等的实现

Asyncio 的 public API 提供了两个用于消费的抽象层：旧的 transport/protocol layer modeled after Twisted, and the newer streams layer. In new code, you almost certainly want to use the streams API, i.e. call asyncio.start_server 和避免原始套接字。这显着减少了行数：

import asyncio, socket

async def handle_client(reader, writer):
    request = None
    while request != 'quit':
        request = (await reader.read(255)).decode('utf8')
        response = str(eval(request)) + '\n'
        writer.write(response.encode('utf8'))
        await writer.drain()
    writer.close()

async def run_server():
    server = await asyncio.start_server(handle_client, 'localhost', 15555)
    async with server:
        await server.serve_forever()

asyncio.run(run_server())

Answer 2

我已经阅读了上面的答案和评论，试图弄清楚如何将 asynchio 库用于套接字。正如 Python 经常发生的那样，官方文档和示例是有用信息的最佳来源。我从支持文章末尾提供的示例中了解了 Transports and Protocols (low-level API), and Streams（高级 API）。

例如，TCP 回显服务器：

import asyncio


class EchoServerProtocol(asyncio.Protocol):
    def connection_made(self, transport):
        peername = transport.get_extra_info('peername')
        print('Connection from {}'.format(peername))
        self.transport = transport

    def data_received(self, data):
        message = data.decode()
        print('Data received: {!r}'.format(message))

        print('Send: {!r}'.format(message))
        self.transport.write(data)

        print('Close the client socket')
        self.transport.close()


async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    server = await loop.create_server(
        lambda: EchoServerProtocol(),
        '127.0.0.1', 8888)

    async with server:
        await server.serve_forever()


asyncio.run(main())

和 TCP Echo 客户端：

import asyncio


class EchoClientProtocol(asyncio.Protocol):
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost

    def connection_made(self, transport):
        transport.write(self.message.encode())
        print('Data sent: {!r}'.format(self.message))

    def data_received(self, data):
        print('Data received: {!r}'.format(data.decode()))

    def connection_lost(self, exc):
        print('The server closed the connection')
        self.on_con_lost.set_result(True)


async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    on_con_lost = loop.create_future()
    message = 'Hello World!'

    transport, protocol = await loop.create_connection(
        lambda: EchoClientProtocol(message, on_con_lost),
        '127.0.0.1', 8888)

    # Wait until the protocol signals that the connection
    # is lost and close the transport.
    try:
        await on_con_lost
    finally:
        transport.close()


asyncio.run(main())

希望它能帮助搜索 asynchio.

的简单解释的人

Python 使用 asyncio 的简单套接字 client/server

Python simple socket client/server using asyncio

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