How to force OS to free port with python

Question

I use a port in my python program and close it,now I want to use it again.Just that port not another port.
Is there any way to force OS to free port with python?

#!/usr/bin/python           # This is server.py file 

import socket               # Import socket module

s = socket.socket()         # Create a socket object
host = socket.gethostname() # Get local machine name
port = 12349
portt = 12341               # Reserve a port for your service.

s.bind((host, portt))        # Bind to the port

s.connect((host, port))
s.close

ss = socket.socket()         # Create a socket object
host = socket.gethostname() # Get local machine name 
ss.bind((host, portt))

s.close

but the output is:

Traceback (most recent call last):
  File "client.py", line 17, in <module>
    ss.bind((host, portt))
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
socket.error: [Errno 98] Address already in use

Answer 1

You'll never be able to force the OS (with any sort of reasonable effort) to release a socket.

Instead you just want to say you don't care with setsockopt

s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

This means that the option takes place at the Socket Object Level SOCKET (as opposed to the TCP or something else) and you're setting the Socket Option REUSEADDR (you're telling the OS that it's OK, you really do want to listen here). And finally, you're turning the option on with 1, rather than off (with 0).