import socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
  s.bind(('127.0.0.1', 8025))
  s.listen(1)
  conn, addr = s.accept()
  with conn:
    print('connected by', addr)
    conn.sendall(b'554 Nope.\r\n')
    while True:
      data = conn.recv(1024)
      if not data: break
      print('received', data)
      conn.sendall(b'503 bad sequence of commands\r\n')