CODEWITHSUNDEEP
pythonsocketstcpsubprocessclient-server
HotWheels
HotWheels

Reputation: 444

Python Client-Server how to handle timeout

I have a TCP client-server where a client sends out shell commands to a server and the server responds with the output of said command. Some of the commands such as date or cd don't work because they are interactive I assume and my code doesn't handle it. Whenever I send said commands, my client seems to hang and just says sending... with my server never receiving anything.

I want to figure out how I can handle this with possibly a timeout where if it takes more than 5 seconds to send out a command, the client will cause a timeout or simply handle it and print an message saying the command did not execute successfully while keeping the client connected to the server.

Here is my code

Client:

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()

Server:

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()

Upvotes: 1

Views: 1426

Answers (1)

Jeremy Friesner
Jeremy Friesner

Reputation: 73304

There are various ways to do it, but probably the easiest way is to call the subprocess.check_output() method, which allows you to specify a timeout value in seconds, and also returns the text that the child process generated, i.e.:

[...]

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))

[...]

Upvotes: 1

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