Simple TCP EchoServer in Python

Question

I found this script of TCP server which "echoes" back the data to the client.

#!/usr/bin/env python 

import socket

host = ''
port = 50000
backlog = 5 
size = 1024 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
s.bind((host,port)) 
s.listen(backlog) 
while 1: 
    client, address = s.accept() 
    data = client.recv(size) 
    if data: 
        client.send(data) 
    client.close()

I'm trying to test & understand it before I will be able to do something on my own and modify, but I'm having some problems. When I'm trying to run the .py script I get the following error in my Terminal (using Ubuntu 14.04 LTS)

> Traceback (most recent call last):
  File "echo.py", line 14, in <module>
    s.bind((host,port))
  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

My Python version is 2.7.6

is there something wrong with the code or I'm doing something wrong?

UPDATE:

it gets worse, any script I run with bind(host, port) gives me the same error.

any help would be appreciated

Answer 1

Perhaps you accidentally ran the EchoServer twice in different windows? You can only bind one receiver to a port/address combination.

Answer 2

Seems like there is some other application running on those ports.

Can you try checking if there are any other app listening on same port using:

netstat -ntlpu | grep 50000

Answer 3

To bind a server it's a little confusing but you have to use a tuple. The correct way is server.bind((host, port))