text: #!/usr/bin/env python3
  #
  #  Copyright (c) 2021, The OpenThread Authors.
  #  All rights reserved.
  #
  #  Redistribution and use in source and binary forms, with or without
  #  modification, are permitted provided that the following conditions are met:
  #  1. Redistributions of source code must retain the above copyright
  #     notice, this list of conditions and the following disclaimer.
  #  2. Redistributions in binary form must reproduce the above copyright
  #     notice, this list of conditions and the following disclaimer in the
  #     documentation and/or other materials provided with the distribution.
  #  3. Neither the name of the copyright holder nor the
  #     names of its contributors may be used to endorse or promote products
  #     derived from this software without specific prior written permission.
  #
  #  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  #  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  #  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  #  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  #  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  #  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  #  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  #  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  #  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  #  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  #  POSSIBILITY OF SUCH DAMAGE.
  #
  import socket
  import sys
  import ipaddress
  
  # USAGE: python3 udp_send.py [destination_ipv6] [destination_port] [message] [hop_limit]
  # udp_send sends a udp packet to an ipv6 address.
  
  
  def main():
      args = sys.argv[1:]
      assert len(args) == 4
      destination_ipv6 = args[0]
      destination_port = args[1]
      message = bytes(args[2], 'utf-8')
      hop_limit = int(args[3])
      sock = socket.socket(
          socket.AF_INET6,  # Internet
          socket.SOCK_DGRAM)  # UDP
  
      address = ipaddress.ip_address(destination_ipv6)
      if address.is_multicast:
          sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_HOPS, hop_limit)
      else:
          sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_UNICAST_HOPS, hop_limit)
      sock.sendto(message, (destination_ipv6, int(destination_port)))
      sock.close()
  
  
  if __name__ == '__main__':
      main()
  