import optparse
import io
import socket
import sys
import time

def ClientRepro(port):

	def EchoChunk(c, data):
		l = len(data)
		c.send(str(l).encode() + b'\r\n')
		c.send(data)
		print("Asking for {0} bytes of data.".format(l))
		response = c.recv(l)
		if data != response:
			raise UserWarning('Echoed data does not match.')
		else:
			print("Successfully echoed {0} byte chunk.".format(l))

	s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	s.connect(('127.0.0.1', port))

	for chunkSize in ( 1, 2, 4, 16, 32, 64, 100, 1000, 2000, 20000 ):
		EchoChunk(s, ('A'*chunkSize).encode()) # Works

	EchoChunk(s, ('A'*io.DEFAULT_BUFFER_SIZE).encode()) # Server Hangs

	s.close()

def ServerRepro(port):

	s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	s.bind(('127.0.0.1', port))
	s.listen(1)
	connection, addr = s.accept()

	# We create a file object from an underlying blocking socket.
	#
	f = connection.makefile('rb')

	while True:
		lengthLine = f.readline()
		if not lengthLine:
			break
		length = int(lengthLine.strip())
		if length:
			print("Reading {0} byte chunk.".format(length))

			# The bug is triggered here, when we've previously
			# received some data (a buffer exists for the input,)
			# and we request to read an exact multiple of the block
			# size (or more correctly our final read is a single
			# block that finishes exactly at the end of the input
			# data) -- this causes the BufferedReader to attempt
			# one more read on the socket, which will block
			# forever.
			#
			data = f.read(int(length))
			print("Echoing {0} byte chunk.".format(length))
			connection.send(data)

	connection.close()

parser = optparse.OptionParser()
parser.add_option('-p', '--port',
	default=12345, type=int,
	help='Specify the client/server TCP port to use.')

( opt, arg ) = parser.parse_args()

if len(arg) != 1:
	parser.print_usage()
	sys.exit()

if arg[0] == 'client':
	ClientRepro(opt.port)
elif arg[0] == 'server':
	ServerRepro(opt.port)
else:
	raise UserWarning('Argument must be either "client" or "server"')