Messenger between VM's via CPU execution time

virt_messenger.py

#!/usr/bin/python3
#
# Usage: virt_messenger.py [--debug]
# Support for sending text, however chance of receiving correct characters: ~5-15%.
# Chance could maybe still be improved by sending slower and/or changing the execution time.

import os
import time
import threading
import multiprocessing as mp
import random
import psutil
import sys

def read():
	bits = [0,0,0, 0,0,0,0,0,0,0, 0,0,0]
	t = threading.currentThread()
	letter = ''
	text = ''
	while getattr(t, 'do_run', True):
		s = time.time()
		random.sample(range(1000000000), n)
		e = time.time()
		if (e-s)-i < 0.0001:
			if len(sys.argv) > 1 and sys.argv[1] == '--debug':
				print('\r[reading: 1 ('+str((e-s)-i)+')]   ', end='')
			bits.pop(0)
			bits.append(1)
		else:
			if len(sys.argv) > 1 and sys.argv[1] == '--debug':
				print('\r[reading: 0 ('+str((e-s)-i)+')]   ', end='')
			bits.pop(0)
			bits.append(0)
		out = 0
		if bits[0] == 1 and bits[1] == 0 and bits[2] == 1 and bits[10] == 1 and bits[11] == 0 and bits[12] == 1:
			for bit in bits[3:10]:
				out = (out << 1) | bit
			#if chr(out).isalpha():
			letter = chr(out)
			text += letter
			print('\r'+"Received: "+text+'\n\n> ', end='')
		elif bits[0] == 1 and bits[1] == 1 and bits[2] == 1 and bits[10] == 1 and bits[11] == 0 and bits[12] == 1:
			for bit in bits[3:10]:
				out = (out << 1) | bit
			#if chr(out).isalpha():
			if chr(out) != letter:
				text += chr(out)
				print('\r'+"Received: "+text+'\n\n> ', end='')
		elif bits.count(1) == 13:
			text = ''
		if e-s < 0.1:
			time.sleep(0.1-(e-s))

def send(text):
	for c in text:
		b = bin(ord(c))
		print('Sending bits: '+b[2:]+'\n')
		send_bits('101'+b[2:]+'101')
		send_bits('111'+b[2:]+'101')
	send_bits('1111111111111')

def send_bits(bits):
	for bit in bits:
		if bit == '1':
			procs = list()
			for x in range(0, psutil.cpu_count()):
				p = mp.Process(target=loop, args=([x], 0.1))
				p.start()
				procs.append(p)
			for p in procs:
				p.join()
		else:
			time.sleep(0.1)

def loop(affinity, seconds):
	proc = psutil.Process()
	proc.cpu_affinity(affinity)
	t = time.time() + seconds
	while time.time() < t:
		pass

def get_input():
	while True:
		message = input('> ')
		if message == 'exit':
			os._exit(0)
		if message != '':
			return message
		print('Invalid message\n')

e = 0
s = 0
n = 1
i = 0
while True:
	t = threading.Thread(target=read)
	t.start()
	# Find variable n such that execution time is between about 0.0002 and 0.00025 seconds
	while True:
		if e-s < 0.0002:
			n = n * 2
			s = time.time()
			random.sample(range(1000000000), n)
			e = time.time()
		elif e-s > 0.00025:
			n -= int(n/1.5)
			s = time.time()
			random.sample(range(1000000000), n)
			e = time.time()
		else:
			# Checking if n is valid 100 times in a row
			for x in range(0,100):
				s = time.time()
				random.sample(range(1000000000), n)
				e = time.time()
				if e-s < 0.0002 or e-s > 0.00025:
					break
			else: # Means "no break", thus succeeded
				break
			continue
	i = e-s	
	message = get_input()
	t.do_run = False
	t.join()
	send(message)