Netcat-like UDP Tool in Python

netcat_udp.py

#!/usr/bin/env python3
"""
Netcat-like UDP Tool in Python

This Python script provides a simple and lightweight netcat-like UDP tool that allows users to
send and receive data over UDP using IPv4 and IPv6 addresses. It is designed to be easy to use
and versatile, making it suitable for various networking tasks, including testing, debugging,
and learning purposes.

By following the netcat command-line style, this script offers users a familiar interface for
communicating over UDP. When launched with only a port number, the script will listen for incoming
UDP traffic. When supplied with a target IP address and port, the script will both send and
receive UDP data.

Keywords: Python, Netcat, UDP, Networking, IPv4, IPv6, Socket Programming, Command Line Tool,
          Lightweight, Versatile, Testing, Debugging, Learning

To use this script, run the following commands:

1. For receiving data only:
   python netcat_udp.py <port>

2. For sending and receiving data:
   python netcat_udp.py <port> <target_host> <target_port>

Replace <port> with the desired local port number, <target_host> with the target IPv4 or IPv6
address, and <target_port> with the target port number.
"""
import socket
import sys
import threading

def receiver(recv_sock, port):
    recv_sock.bind(('', port))
    print(f"Listening on UDP port {port}...")

    while True:
        data, addr = recv_sock.recvfrom(4096)
        print(f"Received from {addr}: {data.decode('utf-8')}")

def sender(send_sock, target_addr):
    print(f"Sending data to {target_addr[0]} on UDP port {target_addr[1]}...")

    while True:
        line = input()
        send_sock.sendto(line.encode('utf-8'), target_addr)

def main():
    argc = len(sys.argv)
    if argc != 2 and argc != 4:
        print("Usage: python netcat_udp.py <port> [target_host target_port]")
        sys.exit(1)

    port = int(sys.argv[1])

    recv_sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
    recv_sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, False)

    recv_thread = threading.Thread(target=receiver, args=(recv_sock, port))
    recv_thread.daemon = True # exit when main thread exits
    recv_thread.start()

    if argc == 4:
        target_host = sys.argv[2]
        target_port = int(sys.argv[3])

        addr_info = socket.getaddrinfo(target_host, target_port, socket.AF_UNSPEC, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
        target_family, _, _, _, target_addr = addr_info[0]

        send_sock = socket.socket(target_family, socket.SOCK_DGRAM, socket.IPPROTO_UDP)

        send_thread = threading.Thread(target=sender, args=(send_sock, target_addr))
        send_thread.daemon = True # exit when main thread exits
        send_thread.start()
        send_thread.join()
        

    recv_thread.join()
    

if __name__ == "__main__":
    main()