How to interrupt socket.recv() in python?

Question

I'm developing a small server system and I need to turn the server off whenever I type "exit()" into the console (the input is handled from another thread) I was wondering if there is a way to terminate the main thread while the socket is awaiting data. I've already tried using _thread.interrupt_main() with a keyboardInterrupt exception in a try block but it didn't work. I also tried os._exit() which worked but it doesn't clean up so I decided not to use it. My code:

import socket
import _thread
import os

clear = lambda: os.system("cls")

try:
    Server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    Server.bind(("localhost",port))
    Server.listen(2)
    clear()
    print("--------------------------------------")
    print("Server running on port %s" % str(port))
    print("--------------------------------------")
except Exception:
    print("error while starting server")
    input()
    exit()

def control():
    while True:
        command = input()
        if command == "exit()":
            #interrupt code here

_thread.start_new_thread(control,())

while True:
    con,ip = Server.accept()
    print(str(ip) + " Connected")

    try:
        cmd = str(con.recv(1024).decode())  #<-- interrupt this line
    except Exception:
        print("Error")

@user207421 I get the following error "[WinError 10038] An operation was attempted on something that is not a socket" — BlockCoder, Mar 03 '19 at 03:36
So you got the wrong socket handle, or you had already closed it. — user207421, Mar 03 '19 at 03:46
@user207421 I thought about that but the socket can't be closed because the closing statement is activated when the main loop breaks. And I'm passing the "Server" socket object to the thread as an argument — BlockCoder, Mar 03 '19 at 13:21
Well that's the problem. That's not the socket that is receiving. It is the accepted socket that is doing that. You can't shutdown a listening socket. It doesn't make sense. — user207421, Mar 03 '19 at 14:48
(In order to mark a question as solved here, please just use the acceptance system, as you have done. We do not add [solved] devices to titles here). — halfer, Mar 03 '19 at 22:30

score 3 · Answer 1 · answered Nov 20 '19 at 20:49

3

sock.shutdown(socket.SHUT_RDWR) is quite handy if you have the socket in the main thread and the thread is blocked in recv/recvfrom/etc. The recv call will end up in an exception and you can use that to finish your thread if you need to.

answered Nov 20 '19 at 20:49

debuti

623
2
10
20

score 1 · Accepted Answer · answered Mar 03 '19 at 05:13

Below code does what you want but on a basic level for closing connection of single client. You should restructure your code for handling multiple clients if you wish so. Best idea would be to start new thread for each connection of same socket connection so that you could handle them seperately.

import socket
import _thread
import os

clear = lambda: os.system("cls")
port = 1026
try:
    Server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    Server.bind(("127.0.0.1",1026))
    Server.listen(2)
    print("--------------------------------------")
    print("Server running on port %s" % str(port))
    print("--------------------------------------")
except Exception:
    print("error while starting server")
    input()
    exit()

def control(sock):
    while True:
        command = input()
        if command == "exit()":
            sock.close()
            os._exit(0)
            #interrupt code here


while True:
    con,ip = Server.accept()
    _thread.start_new_thread(control,(con,))
    print(str(ip) + " Connected")

    try:
        cmd = str(con.recv(1024).decode())  #<-- interrupt this line
    except Exception:
        print("Error")

I know about os._exit() but I didn't want to use it because it doesn't call the cleanup handlers and doesn't flush stdio buffers. Is there any other way to do this? — BlockCoder, Mar 03 '19 at 13:16
i have closed the sock connection before os._exit(). You will have to close all the handle before using it. As far as i know atleast regarding sockets you will have to manually take care of them. — mr_pool_404, Mar 03 '19 at 13:56
Check this link out.I think it would be useful. [https://stackoverflow.com/questions/323972/is-there-any-way-to-kill-a-thread] — mr_pool_404, Mar 03 '19 at 14:00
Thanks, I think I will stick to os._exit() for now since this is only for personal use. — BlockCoder, Mar 03 '19 at 14:07

How to interrupt socket.recv() in python?

2 Answers2