Error: nodename nor servname provided, or not known (python sockets)

Question

I am trying to learn how to use sockets using this tutorial:
https://www.tutorialspoint.com/python/python_networking.htm
I have copied the code from the site into my directory and ran it exactly as was done in the tutorial but got errors. Here is the code from the tutorial.

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

import socket               # Import socket module

s = socket.socket()         # Create a socket object
host = 'localhost' # Get local machine name
port = 12345                # Reserve a port for your service.
s.bind((host, port))        # Bind to the port

s.listen(5)                 # Now wait for client connection.
while True:
    c, addr = s.accept()     # Establish connection with client.
    print("asdf")
    c.send('Thank you for connecting')
    c.close()                # Close the connection

and client.py

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

import socket               # Import socket module

s = socket.socket()         # Create a socket object
host = socket.gethostname() # Get local machine name
port = 12345                # Reserve a port for your service.

s.connect((host, port))
print s.recv(1024)
s.close                     # Close the socket when done

These are the console commands I ran:

python server.py &
python client.py

I got this errors after running the command:

Traceback (most recent call last):
  File "client.py", line 9, in <module>
    s.connect((host, port))
  File     "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/soc    ket.py", line 228, in meth
return getattr(self._sock,name)(*args)
socket.gaierror: [Errno 8] nodename nor servname provided, or not known

In case this is helpful, the version of python I am using is Python 2.7.10 and I use a mac that is version 10.12.6

Thanks in advance

Answer 1

From the docs of socket.gethostname:

Return a string containing the hostname of the machine where the Python interpreter is currently executing.

Note: gethostname() doesn’t always return the fully qualified domain name; use getfqdn() for that.

The host IP is not the same as the hostname. You have a couple of options:

1. You can either manually assign host to 0.0.0.0 or localhost

2. You can also query socket.gethostbyname:

   host = socket.gethostbyname(socket.gethostname()) # or socket.getfqdn() if the former doesn't work