Python server "Only one usage of each socket address is normally permitted"

Question

I'm trying to create a very basic server in python that listens in on a port, creates a TCP connection when a client tries to connect, receives data, sends something back, then listens again (and repeats the process indefinitely). This is what I have so far:

from socket import *

serverName = "localhost"
serverPort = 4444
BUFFER_SIZE = 1024

s = socket(AF_INET, SOCK_STREAM)
s.bind((serverName, serverPort))
s.listen(1)

print "Server is ready to receive data..."

while 1:
        newConnection, client = s.accept()
        msg = newConnection.recv(BUFFER_SIZE)

        print msg

        newConnection.send("hello world")
        newConnection.close()

Sometimes this seems to work perfectly well (if I point my browser to "localhost:4444" the server prints out the HTTP GET request and the webpage print the text "hello world"). But I'm getting the following error message sporadically when I try to start the server after closing it in the last few minutes:

Traceback (most recent call last):
  File "path\server.py", line 8, in <module>
    s.bind((serverName, serverPort))
  File "C:\Python27\lib\socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
error: [Errno 10048] Only one usage of each socket address (protocol/network address/port) is normally permitted

I'm programming in python using Windows 7. Any ideas on how to fix this?

Answer 1

On Windows, you can try these steps:

1. check which process uses the port.

# 4444 is your port number
netstat -ano|findstr 4444

you will get something like this:

# 19088 is the PID of the process
TCP    0.0.0.0:4444           *:*                                    19088

2. kill this process

With:

tskill 19088

Or:

taskkill /F /PID 19088

Good luck.