How to exit Python's tcp accept function? [duplicate]

Question

This program cannot exit because the accept function blocks.

What can be done so that the program exits after a timeout even if the accept function is still running?

# taken from https://realpython.com/python-sockets/#echo-server

import socket

HOST = "127.0.0.1"  # Standard loopback interface address (localhost)
PORT = 65432  # Port to listen on (non-privileged ports are > 1023)

def connect ():
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.bind((HOST, PORT))
        print("listening")
        s.listen()
        print("accepting")
        conn, addr = s.accept()             # If these lines are 
        with conn:                          # commented, the program
            print(f"Connected by {addr}")   # exits normally.
            while True:                     # This is why I think
                data = conn.recv(1024)      # that the *accept* function
                if not data:                # is the problem
                    break                   #
                conn.sendall(data)          #

def main():
    connect()

if __name__ == "__main__":
    main()

Mark Tolonen · Accepted Answer · 2023-02-10 06:29:45Z

1

You can set a timeout on the server socket:

>>> import socket
>>> s=socket.socket()
>>> s.bind(('',5000))
>>> s.listen()
>>> s.settimeout(5)  # 5 seconds
>>> s.accept()                          # waits here...
Traceback (most recent call last):      # 5 seconds later...
  File "<stdin>", line 1, in <module>
  File "D:\dev\Python311\Lib\socket.py", line 294, in accept
    fd, addr = self._accept()
               ^^^^^^^^^^^^^^
TimeoutError: timed out

Catch time timeout if you want to implement other behavior. For example:

def accept(s):
    ''' Wait up to 5 seconds for connection.'''
    s.settimeout(5)
    try:
        results = s.accept()
    except TimeoutError:
        return None
    s.settimeout(None)  # disable timeout
    return results

edited Feb 10, 2023 at 6:29

answered Feb 10, 2023 at 6:09

Mark Tolonen

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