Python - 如何检查套接字是否仍然连接

Question

我有以下代码，这是不言自明的：

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(host, port)
s.send("some data")
# don't close socket just yet... 
# do some other stuff with the data (normal string operations)
if s.stillconnected() is true:
    s.send("some more data")
if s.stillconnected() is false:
    # recreate the socket and reconnect
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect(host, port)
    s.send("some more data")
s.close()

如何实现s.stillconnected() 我不想盲目地重新创建套接字。

Answer 1

如果服务器连接不再活动，调用 send 方法将抛出异常，因此您可以使用 try-exception 块尝试发送数据，如果抛出异常则捕获该异常，并重新建立连接：

try:
    s.send("some more data")
except:
    # recreate the socket and reconnect
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect(host, port)
    s.send("some more data")

编辑：根据@Jean-Paul Calderone 的评论，请考虑使用sendall方法，它是发送所有数据或抛出错误的send高级方法，而不是，它是不保证所有数据传输的低级方法数据，或者使用更高级别的模块，例如可以处理套接字生命周期的 HTTP 库。

Answer 2

我用这个变体得到了很好的结果来检查套接字是否关闭（如果你想检查它是否仍然连接，则否定结果）：

import logging
import socket


logger = logging.getLogger(__name__)


def is_socket_closed(sock: socket.socket) -> bool:
    try:
        # this will try to read bytes without blocking and also without removing them from buffer (peek only)
        data = sock.recv(16, socket.MSG_DONTWAIT | socket.MSG_PEEK)
        if len(data) == 0:
            return True
    except BlockingIOError:
        return False  # socket is open and reading from it would block
    except ConnectionResetError:
        return True  # socket was closed for some other reason
    except Exception as e:
        logger.exception("unexpected exception when checking if a socket is closed")
        return False
    return False