Overview:
- A server based on the UDP protocol processes datagrams received from its UDP based clients. Unlike a TCP Server, an UDP server does not maintain a persistent connection that can be used for streaming data to its clients.
- UDP based servers are suitable for message oriented communications where loss of some datagrams is acceptable for both the clients and servers.
- An UDP based network server can be created using the class UDPServer from Python’s socketserver module.
Server Creation:
- A request handler class is required to be defined to handle the incoming UDP messages from the clients.
- A tuple containing the IP address of the server and the port on which it listens needs to be created.
- An instance of UDPServer needs to be constructed by passing the tuple with server IP and port number and the request handler class
- To make the UDP server listen continuously for incoming messages the serve_forever() method should be called.
Handling Request from Clients:
- The DatagramRequestHandler class provides a base from which datagram-based request handlers can be defined.
- In the example program below, the class MyUDPHandler is derived from DatagramRequestHandler.
- The handle()method is overridden which forms the core of the message handling from UDP clients.
- Messages from the clients are read from the rfile attribute.
- Messages are sent to clients by writing to wfile attribute.
- The client part of the UDP client-server program written with the POSIX API is used to test the UDP Server.
Example:
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import socketserver
# define a subclass of UDPServer
class MyUDPHandler(socketserver.DatagramRequestHandler): def handle(self): # Receive a message from a client print("Got an UDP Message from {}".format(self.client_address[0])) msgRecvd = self.rfile.readline().strip() print("The Message is {}".format(msgRecvd))
# Send a message from a client self.wfile.write("Hello UDP Client! I received a message from you!".encode())
server_IP = "127.0.0.1" server_port = 7070
serverAddress = (server_IP, server_port)
serverUDP = socketserver.UDPServer(serverAddress, MyUDPHandler) serverUDP.serve_forever()
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Output – Server Side:
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Got an UDP Message from 127.0.0.1 The Message is b'Hello UDP Server' |
Output – Client Side:
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Message from Server b'Hello UDP Client! I received a message from you!' |