Python packet generator

pktgen.py

# to simulate DGPS generation
# python pktgen.py tb 3784 1 305
# to receive
# python pktgen.py rb 3784 1 305

# to simulate AMP generation
# python pktgen.py tm 13000 2.77 372
# to receive
# python pktgen.py rm 13000 2.77 372

import sys
import socket
import struct
import time
from datetime import datetime, timedelta

MCAST_GROUP = '239.255.192.137'
BCAST_ADDR = '192.168.43.255'
PADDING = '_you_are_something_socially_appropriate'

def generate_packet(length):
	s = ''
	while(len(s) < length):
		s += PADDING
	return s[0:length]

def in_tolerance(constant, value, tolerance):
	if value > (constant - (constant * tolerance)) and value < (constant + (constant * tolerance)):
		return True
	return False

def log(data):
	with open('/tmp/%s_%s_%s.log' % (mode, port, length), 'a') as f:
		f.write('%s - %s, %i, %0.2f, %i - %s\n' % (datetime.now().strftime('%d/%m/%y %H:%M:%S.%f'), mode, port, freq, length, data.rstrip()))

try:
	mode, port, freq, length = sys.argv[1].strip().lower()[:2], int(sys.argv[2]), float(sys.argv[3]), int(sys.argv[4])
except:
	print 'python pktgen.py tb 3784 1 512'
	print 'python pktgen.py rb 3784 1 512'
	print 'python pktgen.py tm 13000 4 1024'
	print 'python pktgen.py rm 13000 4 1024'
	sys.exit(1)

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

if mode == 'tm':
	s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 1)
	addr = MCAST_GROUP
elif mode == 'rm':
	s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
	addrinfo = socket.getaddrinfo(MCAST_GROUP, None)[0]
	group_bin = socket.inet_pton(addrinfo[0], addrinfo[4][0])
	mreq = group_bin + struct.pack('=I', socket.INADDR_ANY)
	s.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
	s.bind(('', port))
elif mode == 'tb':
	s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
	addr = BCAST_ADDR
elif mode == 'rb':
	s.bind(('', port))
else:
	print 'invalid syntax'
	sys.exit(1)

start_time = datetime.now().strftime('%d/%m/%y %H:%M:%S.%f')

if mode in ['rm', 'rb']:
	i = int(s.recvfrom(length + 32)[0].split(PADDING)[0]) + 1
	last_timestamp, resync, last_resync, count, status, history = datetime.now(), 0, 'never', 1, '', []
	log('Receiver started')

while True:
	if mode in ['tm', 'tb']:
		for i in range(0, 128):
			s.sendto(str(i) + generate_packet(length - len(str(i))), (addr, port))
			sys.stderr.write("\x1b[2J\x1b[H")
			print '%s - %scasting %i byte packets to port %i at %.02f Hz' % (start_time, 'multi' if mode == 'tm' else 'broad', length, port, freq)
			print 'Sent "%i" (%i bytes) @ %0.2f Hz' % (i, length, freq)
			time.sleep(1.0 / freq)
	elif mode in ['rm', 'rb']:
		while i < 128:
			period = datetime.now() - last_timestamp
			data = s.recvfrom(length + 32)[0]
			j = int(data.split(PADDING)[0])
			if j == 0:
				if i != j:
					resync += 1
					i = 0
					last_resync = datetime.now().strftime('%d/%m/%y %H:%M:%S.%f')
					log('Needed resync - %i, %0.2f, %i' % (port, freq, length))

			now = datetime.now()

			rxfreq = 1 / (float(str(now - last_timestamp).split(':')[-1]))

			status = 'in sync'
			reasons = ['%i resync%s' % (resync, 's' if resync != 1 else '')]
			if i != j:
				status = 'out of sync'
				reasons += ['sequence']
			if length != len(data):
				status = 'out of sync'
				reasons += ['length']
			if not in_tolerance(freq, rxfreq, 0.01):
				status = 'out of sync'
				reasons += ['frequency']

			avg_freq = 1 / ((last_timestamp - datetime.strptime(start_time, '%d/%m/%y %H:%M:%S.%f')).total_seconds() / count)

			if len(history) >= 10:
				history = history[-10:]

			history += [[str(now).split()[1], str(i), str(j), '%.06f' % period.total_seconds(), '%.02f' % rxfreq]]

			last_timestamp = now

			count += 1

			sys.stderr.write("\x1b[2J\x1b[H")
			print '%s - listening for %scasted %i byte packets to port %i at %.02f Hz' % (start_time, 'multi' if mode == 'rm' else 'broad', length, port, freq)
			print 'Expected "%i" (%i bytes) @ %0.2f Hz' % (i, length, freq)
			print 'Received "%i" (%i bytes) @ %0.2f Hz' % (j, len(data), rxfreq)
			print 'Status: %s - %s' % (status, ', '.join(reasons))
			print 'Last resync: %s' % (last_resync)
			print 'Average frequency: %0.2f Hz' % (avg_freq)
			for record in history:
				print '\t'.join(record)
			log('%s (%s)' % (status, ', '.join(reasons)))

			i += 1
		i = 0

NOTE: You'll need to change the BCAST_ADDR IP to whatever the broadcast address for your network is, and you may want to change the MCAST_GROUP and PADDING variables also (though it's not necessary).