PortScanner.py

#!/usr/bin/python3

import socket
import pyfiglet
import os

# Prints logo
logo_text = pyfiglet.figlet_format("Port Scanner")
print(logo_text)

# Constants
ADDRESS_FAMILY = socket.AF_INET
SOCKET_TYPE = socket.SOCK_STREAM

# Creates socket object
s = socket.socket(ADDRESS_FAMILY, SOCKET_TYPE)

# Gets user input and removes any carriage return characters from the input, if the code is running on Windows OS
if os.name == 'nt': 
    host = input("Please enter the Target IP: ").replace('\r', '') 
    port_range = input("Please enter the port range: ").replace('\r', '')
else:
    host = input("Please enter the Target IP: ")
    port_range = input("Please enter the port range: ")

# Parses user input and validates them
try:
    socket.inet_aton(host) # converts an IPv4 address string to its 32-bit binary format 
except socket.error:
    print("Invalid IP address")
    exit()

try:
    start_port, end_port = map(int, port_range.split('-'))
    if start_port < 1 or end_port > 65535:
        raise ValueError
except (ValueError, socket.error):
    print("Invalid port range")
    exit()

# Define port scanner function
def portScanner(host, port):
    try:
        result = s.connect_ex((host, port)) # s.connect_ex returns an error code if the connection attempt fails
        if result == 0:
            print(f"Port {port} is open")
        else:
            print(f"Port {port} is closed")
    except socket.gaierror:
        print("Hostname could not be resolved")
        exit()
    except socket.error:
        print("Could not connect to server")
        exit()

# Uses a for loop to iterate over the range of ports to scan and invokes the portScanner function to perform the scan
for port in range(start_port, end_port + 1):
    portScanner(host, port)