Using Python's standard socket library, we can accomplish this port-scanning task. We can take three command-line arguments: target host, and start_port and end_port numbers.

Listing 8.4 gives the code for scanning the ports of a remote host, as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 8 
# This program is optimized for Python 2.7.12 and Python 3.5.2. 
# It may run on any other version with/without modifications. 
 
import argparse 
import socket 
import sys 
  
def scan_ports(host, start_port, end_port): 
    """ Scan remote hosts """ 
    #Create socket 
    try: 
        sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM) 
    except socket.error as err_msg: 
        print ('Socket creation failed. Error code:
           '+ str(err_msg[0]) + ' Error mesage: ' + err_msg[1]) 
        sys.exit() 
      
    #Get IP of remote host 
    try: 
        remote_ip = socket.gethostbyname(host) 
    except socket.error as error_msg: 
        print (error_msg) 
        sys.exit() 
      
    #Scan ports 
    end_port += 1 
    for port in range(start_port,end_port): 
        try: 
            sock.connect((remote_ip,port)) 
            print ('Port ' + str(port) + ' is open') 
            sock.close() 
            sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM) 
        except socket.error: 
            pass # skip various socket errors 
 
if __name__ == '__main__': 
    # setup commandline arguments 
    parser = argparse.ArgumentParser(description='Remote
                                            Port Scanner') 
    parser.add_argument('--host', action="store",
                         dest="host", default='localhost') 
    parser.add_argument('--start-port', action="store",
                        dest="start_port", default=1, type=int) 
    parser.add_argument('--end-port', action="store",
                        dest="end_port", default=100, type=int) 
    # parse arguments 
    given_args = parser.parse_args() 
    host, start_port, end_port =  given_args.host, 
    given_args.start_port, given_args.end_port 
    scan_ports(host, start_port, end_port) 

If you execute this recipe to scan your local machine's port 1 to 100 to detect open ports, you will get an output similar to the following:

# python 8_4_scan_port_of_a_remote_host.py --host=localhost --start-port=1 --end-port=100
Port 21 is open
Port 22 is open
Port 23 is open
Port 25 is open
Port 80 is open