How do I abort a socket.recv() from another thread in Python

Question

I have a main thread that waits for connection. It spawns client threads that will echo the response from the client (telnet in this case). But say that I want to close down all sockets and all threads after some time, like after 1 connection.

How would I do it? If I do clientSocket.close() from the main thread, it won't stop doing the recv. It will only stop if I first send something through telnet, then it will fail doing further sends and recvs.

My code looks like this:

# Echo server program
import socket
from threading import Thread
import time

class ClientThread(Thread):
    def __init__(self, clientSocket):
            Thread.__init__(self)
            self.clientSocket = clientSocket

    def run(self):
            while 1:
                    try:
                            # It will hang here, even if I do close on the socket
                            data = self.clientSocket.recv(1024)
                            print "Got data: ", data
                            self.clientSocket.send(data)
                    except:
                            break

            self.clientSocket.close()

HOST = ''
PORT = 6000
serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serverSocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
serverSocket.bind((HOST, PORT))
serverSocket.listen(1)

clientSocket, addr = serverSocket.accept()
print 'Got a new connection from: ', addr
clientThread = ClientThread(clientSocket)
clientThread.start()

time.sleep(1)

# This won't make the recv in the clientThread to stop immediately,
# nor will it generate an exception
clientSocket.close()

Answer 1

I know this is an old thread and that Samuel probably fixed his issue a long time ago. However, I had the same problem and came across this post while google'ing. Found a solution and think it is worthwhile to add.

You can use the shutdown method on the socket class. It can prevent further sends, receives or both.

socket.shutdown(socket.SHUT_WR)

The above prevents future sends, as an example.

See Python docs for more info.

Answer 2

I don't know if it's possible to do what you're asking, but it shouldn't be necessary. Just don't read from the socket if there is nothing to read; use select.select to check the socket for data.

change:

data = self.clientSocket.recv(1024)
print "Got data: ", data
self.clientSocket.send(data)

to something more like this:

r, _, _ = select.select([self.clientSocket], [], [])
if r:
    data = self.clientSocket.recv(1024)
    print "Got data: ", data
    self.clientSocket.send(data)

EDIT: If you want to guard against the possibility that the socket has been closed, catch socket.error.

do_read = False
try:
    r, _, _ = select.select([self.clientSocket], [], [])
    do_read = bool(r)
except socket.error:
    pass
if do_read:
    data = self.clientSocket.recv(1024)
    print "Got data: ", data
    self.clientSocket.send(data)