Python client and server to send and receive files

file_client.py

import socket
import sys
import os


# check arguments
def assert_(cond, message = None, print_help=True):
	if (not cond):
		if (message):
			print()
			print(message)
			print()
		if (print_help):
			print("  Usage: {} file domain-name|ip-address port-number".format(sys.argv[0]))
			print("Example: {} meme.png your_vps.ru 8800".format(sys.argv[0]))
			print("Example: {} video.mp4 18.33.12.49 9332".format(sys.argv[0]))
		exit(0)

assert_(len(sys.argv) == 4, "Wrong number of arguments")
assert_(os.path.isfile(sys.argv[1]), "Could not open file {}".format(sys.argv[1]))


# connect to server
try:
	s = socket.socket()
	s.connect((sys.argv[2], int(sys.argv[3])))
except socket.error:
	assert_(False, "Could not connect to server {}:{}".format(sys.argv[2], sys.argv[3]))


# send filename
s.send(sys.argv[1].rpartition('/')[2].encode('utf-8'))
s.send(b'\x00')


# send the file itself
try:
	data_sent = 0
	file_size = os.path.getsize(sys.argv[1])
	with open(sys.argv[1], 'rb') as f:
		while True:
			data = f.read(1024)
			if (not data): break
			s.send(data)
			data_sent += len(data)
			print("Sent {} out of {} bytes of data ({}%)".format(data_sent, file_size, data_sent/file_size*100))
except IOError:
	assert_(False, "Unknown IO error happened", False)

file_server.py

# This code is based on server_threads.py example from here:
# https://gist.github.com/gordinmitya/349f4abdc6b16dc163fa39b55544fd34

import socket
import sys
import os
from threading import Thread



# thread to listen one particular client
class ClientListener(Thread):
	def __init__(self, sock: socket.socket):
		super().__init__(daemon=True)
		self.sock = sock
		self.file = None

	def assert_(self, cond, message = None):
		if (not cond):
			if (message):
				self.sock.send(message.encode('utf-8'))
				print(message)
			self.sock.close()
			print(self.name + ' disconnected')
			if (self.file):
				self.file.close()
			sys.exit()

	def run(self):
		print("Client's thread:", self.name)

		# Revieve user filename and part of data
		name_and_data = self.sock.recv(1024)
		self.assert_(b'\x00' in name_and_data,
			"Name of file is too long" if len(name_and_data) == 1024 else "Reveived data is in wrong format")
		name_and_data = name_and_data.partition(b'\x00') # separate name from data
		data = name_and_data[2]
		user_filename = name_and_data[0].decode('utf-8').rpartition('/')[2]

		# Check for filename collisions
		real_filename = user_filename
		user_filename = user_filename.rpartition('.') # to separate the extension
		i = 0
		while (os.path.isfile(real_filename)):
			i+=1
			real_filename = "{}_copy{}.{}".format(user_filename[0], i, user_filename[2])

		# Try to create file
		try:
			self.file = open(real_filename, 'wb')
		except IOError:
			self.assert_(False, "Could not create file {}".format(real_filename))

		# Save data to the file
		while True:
			self.file.write(data)
			data = self.sock.recv(1024)
			if (not data): break

		# Finish the thread
		self.assert_(False) 



# main part

def main():
	sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # IPv4 TCP
	# sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
	sock.bind(('', 8800))
	sock.listen()
	while True:
		# blocking call, waiting for new client to connect
		conn, addr = sock.accept()
		print('New client connected:', str(addr))
		ClientListener(conn).start()


if __name__ == "__main__":
	main()