connected-udp-datagram.py

# Run this tool and feed it stuff.
# $ python3 udp-test.py
#
# Emulate a remote client sending data:
# $ cat /dev/urandom | nc -u 127.0.0.1 7502
#
# Cancel netcat and try again, second attempt will fail because the source port
# likely changed (not guaranteed, but statistically likely)
#

import socket

udp_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
udp_socket.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 2 ** 16)
udp_socket.bind(('127.0.0.1', 7502))

PACKET_SIZE_BYTES = 16

# Read address of first packet and only allow future data to come from that
_, addr = udp_socket.recvfrom(0)
udp_socket.connect(addr)

while True:
    # Don't use recvfrom, we know who the source is because of connect()
    packet = udp_socket.recv(PACKET_SIZE_BYTES)
    print(packet)