Python客户端-服务器如何处理超时

Question

我有一个 TCP 客户端-服务器，客户端向服务器发送 shell 命令，服务器以所述命令的输出进行响应。某些命令（例如 date 或 cd ）不起作用，因为我假设它们是交互式的，而我的代码无法处理它。每当我发送所述命令时，我的客户端似乎挂起，只是说发送......而我的服务器从未收到任何东西。

我想弄清楚如何在可能出现超时的情况下处理这个问题，如果发送命令的时间超过 5 秒，客户端将导致超时或简单地处理它并打印一条消息，说明命令没有在保持客户端连接到服务器的同时成功执行。

这是我的代码

客户：

import socket


# Client
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  # creates TCP Socket

# local host and port
LOCAL_HOST = '127.0.0.1'

PORT = 5313
BUFFER_SIZE = 5000  # size of message

sock.settimeout(5)

# connect socket to ip and port
sock.connect((LOCAL_HOST, PORT))
print("Connected to server\n")
print("Enter quit to close connection\n")
while True:

    message = input("Please enter a command:\n")  # ask user to input message
    if message == 'quit':
        break
    if len(message) == 0:
        print("Please enter something")
        message = input("Please enter a command:\n")
    print("Sending %s" % message)
    sock.send(str.encode(message))  # send message
    command = str(sock.recv(BUFFER_SIZE), "utf-8")  # receive message

    print("received %s" % command)
print("closing connection with server")
sock.close()

服务器：

import socket
import subprocess


# Server
# Some commands do not work such as cd. Date does not work on windows because it is interactive.

# creates TCP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

sock.settimeout(5)

# port and server ip(localhost)
LOCAL_HOST = ''
PORT = 5313

BUFFER_SIZE = 5000  # size of message

# test connection
print("Server starting up on %s with port number %s" % (LOCAL_HOST, PORT))
# bind socket to ip and port
sock.bind((LOCAL_HOST, PORT))
# listen to socket
sock.listen(1)

# socket will accept connection and client address

print("Waiting for connection")  # waiting for connection
connection, address = sock.accept()  # accept connection with client address
print("Connected to", address)  # connected by address
while True:

    command = connection.recv(BUFFER_SIZE)  # receive message from client

    if not command:
        break

    if len(command) > 0:

        terminal = subprocess.Popen(command[:].decode("utf-8"), shell=True, stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE, stdin=subprocess.PIPE)
        output = terminal.stdout.read() + terminal.stderr.read()
        output_as_string = str(output, "utf-8")
        connection.send(str.encode("0:") + str.encode(output_as_string))
        print(output_as_string)

print("Closing Server")
sock.close()
connection.close()

Answer 1

有多种方法可以做到，但可能最简单的方法是调用subprocess.check_output() 方法，它允许您指定以秒为单位的超时值，并且还返回子进程生成的文本，即：

[...]

while True:
    command = connection.recv(BUFFER_SIZE)  # receive message from client
    if not command:
        break
    command = command.decode("utf-8").strip()
    if len(command) > 0:
        try:
           output_as_string = subprocess.check_output(command, stderr=subprocess.STDOUT, shell=True, timeout=5.0).decode("utf-8")
        except subprocess.TimeoutExpired:
           output_as_string = "Sub-process timed out!\r\n"

        connection.send(str.encode("0:") + str.encode(output_as_string))

[...]