linux-nc-and-python-sockets

nc or netcat lets you create socket servers or connect to services via sockets.

The nc man page is excellent. This first thing I tried was creating a simple-chat like program between two terminals.

Simple nc chat application

Start listening (nc -l) for a connection on a port (31337).

On terminal A

nc -l 31337

Connect to (127.0.0.1) on a port (31337).

On terminal B

nc 127.0.0.1 31337

Like the man page suggests all text submitted on either terminal A or B will appear on both terminals. Conventionally the server "listening" for connections is typically labeled the server. In this case neither terminal is a server because if either closes, both close...

Use python to interact with nc

On terminal A

nc -l 31337

On terminal b

python

>>> import socket
>>> s = socket.socket( socket.AF_INET, socket.SOCK_STREAM )
>>> s.connect( ( 'localhost', 31337 ) )
>>> s.send( 'python says hello nc' )
20
>>> s.recv( 30 )
'nc says hello python\n'
>>> # To learn more about sockets do:
>>> help( s )
>>> # when you are finished run s.close()

The constant socket.AF_INET creates a socket which allows us to connect to an ip/name and port. The constant socket.AF_UNIX creates a socket which allows us to connect via files? socket.SOCK_STREAM is the type of socket (tcp/ip). socket.SOCK_DGRAM (data-gram or UDP)