Python 3.4+Async programmingterm

asyncio.Protocol

protocols and transports

The protocol for a stream connection (TCP, Unix socket, SSL): the loop calls data_received() for every chunk of bytes and eof_received() at the end.

Syntax

transport, protocol = await loop.create_connection(ProtocolClass, host, port)

Learners rarely need this layer: streams (asyncio.open_connection() and asyncio.start_server()) cover TCP, and asyncio.create_subprocess_exec() covers processes. The main trap: data_received() knows nothing about message boundaries — one sent message may arrive in two chunks and two may arrive as one, so buffering and delimiter search are yours to write (StreamReader ships readline() and readuntil()). A protocol pays off only when you need raw speed without extra coroutines.

Examples

import asyncio
import socket
class Echo(asyncio.Protocol):
    def connection_made(self, transport):
        self.transport = transport
    def data_received(self, data):
        print('получено', data)  # → получено b'ping'
        self.transport.write(data.upper())
async def main():
    loop = asyncio.get_running_loop()
    left, right = socket.socketpair()  # локальная пара сокетов вместо сети
    transport, proto = await loop.create_connection(Echo, sock=left)
    right.sendall(b'ping')
    await asyncio.sleep(0.01)
    print(right.recv(10))  # → b'PING'
    transport.close()
    right.close()
asyncio.run(main())

See also

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