##
7.2.2 Example

Here are two minimal example programs using the TCP/IP protocol: a server that echoes all data that it receives back (servicing only one client), and a client using it. Note that a server must perform the sequence `socket()`, `bind()`, `listen()`, `accept()` (possibly repeating the `accept()` to service more than one client), while a client only needs the sequence `socket()`, `connect()`. Also note that the server does not `send()`/`recv()` on the socket it is listening on but on the new socket returned by `accept()`.

      # Echo server program
      import socket

      HOST = ''                 # Symbolic name meaning the local host
      PORT = 50007              # Arbitrary non-privileged port
      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()

      # Echo client program
      import socket

      HOST = 'daring.cwi.nl'    # The remote host
      PORT = 50007              # The same port as used by the server
      s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
      s.connect((HOST, PORT))
      s.send('Hello, world')
      data = s.recv(1024)
      s.close()
      print 'Received', `data`