how to close a blocking socket while it is waiting to receive data?

Question

I have a service that uses a blocking socket to receive data. The problem I have is that I do not know how to properly close the socket if it is still waiting for data. Below is a short snip of how I am opening and waiting for data: I do not want to implement timeouts as according to the python documentation the socket must be blocking in order to use makefile.

I may be going about this completely wrong as I am new to programming with sockets.

EDIT:

It should be noted that the I cannot alter how the server operates.

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
reader = s.makefile("rb")
line = reader.readline()

Answer 1

There is a quite simple solution. Given a socket and a reader file object like rfile = socket.makefile('rb'), in order to make rfile.readline() return immediately when the socket is closed, you need to execute the following in a separate thread:

socket.shutdown(socket.SHUT_RDWR)
socket.close()

Calling socket.shutdown() will make rfile.readline() return an empty str or bytes, depending on the version of Python (2.x or 3.x respectively).

Answer 2

One solution to close this socket is to ask the server to close it.

If server close the client socket, the client will receive a "Connection reset by peer" error, and it may break the blocking receive.

Another solution would be to not use readline() and put a timeout on your socket (indefinite wait could wait.... indefinitely)