非阻塞Python套接字如何接收输入?

时间:2020-03-24 22:06:09

标签: python sockets

如果我有与名为sock的解锁套接字相关的代码

recv_data = sock.recv(1024)
        if recv_data:
            data.outb += recv_data
        else:
            print('closing connection to', data.addr)
            sel.unregister(sock)
            sock.close()

究竟会发生什么?语句recv_data = sock.recv(1024)与阻塞和非阻塞有何不同?如果程序不等待该语句完成,那么recv_data会有什么价值?

编辑: 完整的服务器代码:

import selectors
import socket
import types

host = "127.0.0.1"
port = 65432

def accept_wrapper(sock):
    conn, addr = sock.accept()
    print('accepted conneciton from', addr)
    conn.setblocking(False)
    data = types.SimpleNamespace(addr=addr, inb=b'', outb=b'')
    events = selectors.EVENT_READ | selectors.EVENT_WRITE
    sel.register(conn, events, data=data)

def service_connection(key, mask):
    sock = key.fileobj
    data = key.data
    if mask & selectors.EVENT_READ:
        recv_data = sock.recv(1024)
        if recv_data:
            data.outb += recv_data
        else:
            print('closing connection to', data.addr)
            sel.unregister(sock)
            sock.close()
    if mask & selectors.EVENT_WRITE:
        if data.outb:
            print('echoing', repr(data.outb), 'to', data.addr)
            sent = sock.send(data.outb)
            data.outb = data.outb[sent:]

sel = selectors.DefaultSelector()
lsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
lsock.bind((host, port))
lsock.listen()
print('listening on', (host, port))
lsock.setblocking(False)
sel.register(lsock, selectors.EVENT_READ, data=None)

while True:
    events = sel.select(timeout=None)
    for key, mask in events:
        if key.data is None:
            # From the listening socket
            accept_wrapper(key.fileobj)
        else:
            # Client Socket
            service_connection(key, mask)

1 个答案:

答案 0 :(得分:0)

如果sock是非阻塞的,否则它将阻塞BlockingIOError。代码周围是否没有显示try / except?另一个选项是select.select,用于确保在调用recv之前读取了要接收的数据。

示例假设合适的服务器:

>>> from socket import *
>>> s=socket()
>>> s.connect(('localhost',5000))
>>> s.setblocking(0)
>>> s.recv(1024)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
BlockingIOError: [WinError 10035] A non-blocking socket operation could not be completed immediately

编辑:

使用附加代码,仅在recv报告sel.select(准备读取的数据)时调用EVENT_READ,因此recv不应阻塞。它将返回数据或一个空字符串。后者表明套接字已关闭。