Port Scanner in Python

Tutorial Difficulty Level    

This post will show how you can make a small and easy-to-use port scanner program written in Python. There are many ways of doing this with Python, but we’re going to do it using the built-in module Socket.

Do not run programs like this one against servers in the college. Behaviour like this could be seen as malicious and get you suspended!

Sockets

The socket module in Python provides access to the BSD socket interface.

It includes the socket class, for handling the actual data channel, and functions for network-related tasks such as converting a server’s name to an address and formatting data to be sent across the network.

Sockets are widely used on the Internet, as they are behind any kind of network communications done by your computer.

The INET sockets, account for at least 99% of the sockets in use.

The web browser’s that you use opens a socket and connects to the web server.

Any network communication goes through a socket.

Socket functions

Before we get started with our sample program, let’s see some of the socket functions we are going to use.

sock = socket.socket (socket_family, socket_type)
Syntax for creating a socket

sock = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
Creates a stream socket

AF_INET
Socket Family (here Address Family version 4 or IPv4)

SOCK_STREAM
Socket type TCP connections

SOCK_DGRAM
Socket type UDP connections

gethostbyname(“host”)
Translate a host name to IPv4 address format

socket.gethostbyname_ex(“host”)
Translate a host name to IPv4 address format, extended interface

socket.getfqdn(“8.8.8.8”)
Get the fqdn (fully qualified domain name)

socket.gethostname()
Returns the hostname of the machine..

socket.error
Exception handling

Making a program using Python Sockets

This small port scanner program will try to connect on every port you define for a particular host.

The first thing we must do is import the socket library and other libraries that we need.

Open up an text editor, copy & paste the code below. Save the file as “portscanner.py” and exit the editor:

Let’s run the program and see how the output can look:

W00t!