3 classes in Java which implement system independent datagram communication?

Question

I'm revising for a network exam and this is one of the questions in a few past papers.

Name 3 classes in Java which implement system independent datagram communication?

I was led to believe there were only 2 class to implement system independent datagram communication;

• DatagramPacket
• DatagramSocket

What could the 3rd class be?

Answers greatly appreciated

Answer 1

The java.net package contains three classes to help you write Java programs that use datagrams to send and receive packets over the network:

DatagramSocket, DatagramPacket, and MulticastSocket

public class MulticastSocket extends DatagramSocket

An application can send and receive DatagramPackets through a DatagramSocket. In addition, DatagramPackets can be broadcast to multiple recipients all listening to a MulticastSocket.

The multicast datagram socket class is useful for sending and receiving IP multicast packets. A MulticastSocket is a (UDP) DatagramSocket, with additional capabilities for joining "groups" of other multicast hosts on the internet.

A multicast group is specified by a class D IP address and by a standard UDP port number. Class D IP addresses are in the range 224.0.0.0 to 239.255.255.255, inclusive. The address 224.0.0.0 is reserved and should not be used.

Answer 2

According to the Java Trails, it looks like you're missing the MulticastSocket, which would allow you to listen to requests coming in from multicast addresses.