Simple NCAT Implementation

simple_ncat.py

from argparse import ArgumentParser, RawDescriptionHelpFormatter
from socket import socket, AF_INET, SOCK_STREAM

# configuring arguments
parser = ArgumentParser(description="Portable NCAT",
                        formatter_class=RawDescriptionHelpFormatter)

parser.add_argument("-l",
                    "--listen",
                    action="store_true",
                    default=False,
                    dest="listen",
                    help="sets the program on listening mode")
parser.add_argument("-c",
                    "--connect",
                    action="store_true",
                    default=False,
                    dest="connect",
                    help="sets the program on connecting mode")

parser.add_argument("-P",
                    help="sets the port",
                    metavar="PORT_NUMBER",
                    type=int,
                    dest="PORT",
                    required=True)

parser.add_argument("-H",
                    help="sets the host",
                    metavar="HOSTNAME",
                    dest="HOST",
                    required=True)
# parsing the args
args = parser.parse_args()

# safeguarding
if args.connect and args.listen:
    raise ValueError("Method not allowed")

# if selected connect mode
if args.connect:
    # instantiate the socket
    client = socket(AF_INET, SOCK_STREAM)

    # performing safe connection
    try:
        client.connect((args.HOST, args.PORT))
        print("[#] Connected to the Server")
    except ConnectionRefusedError:
        print("[X] Unable to Connect To: tcp://%s:%d" % (args.HOST, args.PORT))
        exit(1)

    # iterate on connction
    while True:
        # recieve message from server
        data = client.recv(4096).decode()

        # exit if no data
        if not data:
            client.close()
            break

        # printining the response on client
        print("SERVER>", data)

        # getting the client info
        data = input("CLIENT> ")

        # sending on the server
        client.sendall(data.encode())
    pass
elif args.listen:
    # instantiate server
    server = socket(AF_INET, SOCK_STREAM)

    # safe binding host and port
    try:
        server.bind((args.HOST, args.PORT))
        print("[#] Server will listen on: tcp://%s:%d" %
              (args.HOST, args.PORT))
    except OSError:
        print("[#] Port already in use")
        exit(1)

    # listening to the server
    server.listen()
    print("[#] Listening")

    # iterating
    while True:
        # accepting the connection
        client, address = server.accept()
        print("[!] Client Connected: tcp://%s:%d" % (address[0], address[1]))

        # iterating while client is available
        while True:
            # trying to send data
            try:
                # getting input
                data = input("SERVER> ")

                # sending it to the client
                client.sendall(data.encode())

                # receving from the client
                data = client.recv(4096).decode()

                # disconnect if no data recieved
                if not data:
                    print("[!] Client Disconnected: tcp://%s:%d" %
                          (address[0], address[1]))
                    client.close()
                    break
                # print the client data
                print("CLIENT>", data)
            except Exception:
                print("[!] Client Disconnected: tcp://%s:%d" %
                      (address[0], address[1]))

    pass