new_contents: # Echo server program
  import socket
  
  HOST = ''                 # Symbolic name meaning all available interfaces
  PORT = 4444              # Arbitrary non-privileged port
  with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
      s.bind((HOST, PORT))
      s.listen(1)
      conn, addr = s.accept()
      with conn:
          print('Connected by', addr)
          while True:
              data = conn.recv(1024)
              if not data: break
              conn.sendall(data)
  
subject: Add an echo server program for local testing