Mar. 07, 2013

Port scanner in Python

Overview

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, and I'm going to do it using the
built-in module Socket.

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. Source

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.

For more reading about the socket module, please see the official documentation.

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

How to make a simple port scanner program in Python

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

#!/usr/bin/env python
import socket
import subprocess
import sys
from datetime import datetime

# Clear the screen
subprocess.call('clear', shell=True)

# Ask for input
remoteServer    = raw_input("Enter a remote host to scan: ")
remoteServerIP  = socket.gethostbyname(remoteServer)

# Print a nice banner with information on which host we are about to scan
print "-" * 60
print "Please wait, scanning remote host", remoteServerIP
print "-" * 60

# Check what time the scan started
t1 = datetime.now()

# Using the range function to specify ports (here it will scans all ports between 1 and 1024)

# We also put in some error handling for catching errors

try:
    for port in range(1,1025):  
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        result = sock.connect_ex((remoteServerIP, port))
        if result == 0:
            print "Port {}: 	 Open".format(port)
        sock.close()

except KeyboardInterrupt:
    print "You pressed Ctrl+C"
    sys.exit()

except socket.gaierror:
    print 'Hostname could not be resolved. Exiting'
    sys.exit()

except socket.error:
    print "Couldn't connect to server"
    sys.exit()

# Checking the time again
t2 = datetime.now()

# Calculates the difference of time, to see how long it took to run the script
total =  t2 - t1

# Printing the information to screen
print 'Scanning Completed in: ', total

Sample output

Let's run the program and see how an output can look like


$ python portscanner.py

Enter a remote host to scan: www.your_host_example.com
------------------------------------------------------------
Please wait, scanning remote host xxxx.xxxx.xxxx.xxxx
------------------------------------------------------------

Port 21:   Open
Port 22:    Open
Port 23:    Open
Port 80:    Open
Port 110:   Open
Port 111:   Open
Port 143:   Open
Port 443:   Open
Port 465:   Open
Port 587:   Open
Port 993:   Open
Port 995:   Open

Scanning Completed in:  0:06:34.705170

Disclaimer

This program is intended for individuals to test their own equipment for weak
security, and the author will take no responsibility if it is put to any other use

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Read more about:

Ahmed Elshaer Jan. 11, 2014, 2:59 p.m.

i was trying this code on my machine but my antivirus alerts me that a port scanning is up on my machine from my VM , and the script didnot respond and no output came out , can anyone tell me what happened and how to scan without antivirus stop it ???
basu Nov. 13, 2013, 1:03 a.m.

thank u
Jython Sept. 27, 2013, 5:23 p.m.

The code posted had some errors. Use this code below it works fine.

import socket
import subprocess
import sys
from datetime import datetime

## Clear the screen
subprocess.call('clear', shell=True)

## Enter Host to scan
remoteServer = input("Enter a remote host to scan: ")
remoteServerIP = socket.gethostbyname(remoteServer)

#This is just a nice touch that prints out information on which host we are about to scan
print("-" * 60)
print "Please wait, scanning remote host", remoteServerIP)
print("-" * 60)

## Check what time the scan started
t1 = datetime.now()

## Using the range function to specify ports (here it will scans all ports between 1 and 1024)

## We also put in some error handling for catching errors

try:
for port in range(1,1025):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
result = sock.connect_ex((remoteServerIP, port))
if result == 0:
## if a socket is listening it will print out the port number
print("Port {}: Open".format(port))
sock.close()

## Dont press any buttons or you will screw up the scanning, so i added a keyboard exception
except KeyboardInterrupt:
print("You pressed Ctrl+C")
sys.exit()
## Here is my host execption, incase you typed it wrong. ( i guess mayeb i should have added this up top)
except socket.gaierror:
print("Hostname could not be resolved. Exiting")
sys.exit()
## finally socket error incase python is having trouble scanning or resolving the port
except socket.error:
print("Couldn't connect to server")
sys.exit()

## Checking the time again
t2 = datetime.now()

## Calculates the difference of time, to see how long it took to run the script
total = t2 - t1

## Printing the information to screen
print('Scanning Completed in: ', total)
FranklenS Sept. 11, 2013, 1:29 p.m.

This is an excellent intro to sockets and for me as a pure novice has been extremely helpful. Thanks for that.

I have one question though. The scan seems to take a very long time, is there a way to increase the speed by running scans on multiple ports concurrently or using a method other than connect?
Armoros Sept. 11, 2013, 12:40 p.m.

Very nice tutorial
Thomas Sept. 6, 2013, 10:55 a.m.

Thank you for helping me understand socket programming.

As a small improvement to the script I would suggest the following:

Instead of writing the exceptions like this:

except socket.error:
print "Couldn't connect to server"
sys.exit()

I would write:

except socket.error:
sys.exit("Couldn't connect to server")

This has the following advantages:

- The return value to the Shell is "failure" instead of success.
- The error message (should) be written to the error stream instead of standard out.
- It is shorter :-)
Teodor Georgiev Aug. 24, 2013, 12:48 p.m.

Actually it is a really simple port scanner as it doesn't implement any async i/o method (select / poll / epoll)
loberts Aug. 6, 2013, 8:37 a.m.

Use a list. Supposing the ports you want to scan are 21, 22, 35, 43, 558, 795 you can declare the list like so:

portList = [21,22,35,43,558,795]

Then you can replace 'for port in range(1,1025) with:

for port in portList:
#do stuff

The word, 'port' in the code above is just you giving the item a variable name, it can be 'for Johan in portList:' if you really wanted.

See image: http://i.imgur.com/9p9Z1Mc.png
Johan Badenhorst Aug. 6, 2013, 4 a.m.

I am really new to python (so new that I have never attempted coding in it... but I found this post and it seems like the easiest way to achieve what I am looking for) I and was wondering if anyone would be willing to help.

I need this code to scan only certain ports (I have 6) which can be manually put into the code and then run continuously in a loop.

This: for port in range(1,1025): tells python to give "port" the value of 1 to 1025 right? How do I change this complete statement to select only certain ports?

And if someone can please point me in the direction of creating a loop I would be greatful..

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