echo_server.py

#!/usr/bin/python3

import socket

HOST = "localhost"
PORT = 1337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)

conn, addr = s.accept()

print("Connected by", addr)

while 1:
    data = conn.recv(1024)
    if not data: break
    conn.send(data)

conn.close()