import socket
from os.path import exists, splitext
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

	def run(self):
		#getting filename and first piece of file
		#they are splitted by special FS (file separator) character
		chunk = self.sock.recv(1024)
		filename, data = chunk.split(b'\034', 1)
		path = filename.decode('utf-8')
		name, format = splitext(path)
		i = 0
		while exists(path):
			path = name + '_copy' + str('' if i == 0 else i) + format
			i += 1
		with open(path, 'wb+') as file:
			file.write(data)
			while True:
				# try to read 1024 bytes from user
				# this is blocking call, thread will be paused here
				data = self.sock.recv(1024)
				if data:
					file.write(data)
				else:
					# if we got no data – client has disconnected
					file.close()
					print("Connection from", addr, 'is closed')
					# finish the thread
					return


# AF_INET – IPv4, SOCK_STREAM – TCP
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# reuse address; in OS address will be reserved after app closed for a while
# so if we close and immediately start server again – we'll get error
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# listen to all interfaces at 1234 port
sock.bind(('', 1234))
sock.listen()
while True:
	# blocking call, waiting for new client to connect
	con, addr = sock.accept()
	print("Connection from", addr)
	# start new thread to deal with client
	ClientListener(con).start()