import socket
import json
import sys
import time

'''
testing procedure:

python udp_sender.py small fast  # small UDP packet reaches destination
ip route get to 10.10.10.10
python udp_sender.py big fast    # big UDP packet does not reach destination
ip route get to 10.10.10.10
python udp_sender.py small slow  # small UDP packet reaches destination
ip route get to 10.10.10.10
python udp_sender.py big slow    # big UDP packet does not reach destination
ip route get to 10.10.10.10      # entry is added
python udp_sender.py big fast    # big UDP packet reaches destination
'''

DST_HOST = '10.10.10.10'  # IP of host with mtu smaller then sender one or with MTU reduction in path
DST_PORT = 515            # PORT on dst host
SOURCE_HOST = socket.gethostbyname(socket.gethostname())  # source IP adress, it may not work in every case
SOURCE_PROT = 60000       # source static port for easier packet capture
SLEEP_TIME = 1            # may vary depending network architecture and server speed

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0)
sock.bind((SOURCE_HOST, SOURCE_PROT))
sock.connect((DST_HOST, DST_PORT))

msg = {}
msg['sourcehost'] = socket.getfqdn()
if sys.argv[1] == 'big':
    msg['message'] = "bigmessage_datadatadatadatadatadata\n" * 120  # packet exceeds typical 1500 MTU
else:
    msg['message'] = "smallmessage_datadatadatadatadatadata\n"

sock.send(json.dumps(msg))
if sys.argv[2] == 'slow':
    time.sleep(SLEEP_TIME)
sock.close()
sys.exit(0)