Python - 如何檢查套接字是否仍然連接

Question

我有以下代碼，這是不言自明的：

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()

如何實現s.stillconnected()我不想盲目地重新創建套接字。

Answer 1

如果服務器連接不再活動，調用 send 方法將拋出異常，因此您可以使用 try-exception 塊嘗試發送數據，如果拋出異常則捕獲該異常，並重新建立連接：

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")

編輯：根據@Jean-Paul Calderone 的評論，請考慮使用sendall方法，該方法是發送所有數據或引發錯誤的高級方法，而不是send ，后者是不保證傳輸的低級方法在所有數據中，或者使用更高級別的模塊，例如可以處理套接字生命周期的 HTTP 庫。

Answer 2

我用這個變體得到了很好的結果來檢查套接字是否關閉（如果你想檢查它是否仍然連接，則否定結果）：

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