UDP multicasting

Multicasting is the process of sending a message to multiple clients at the same time. Each client will receive the same message. In order to participate in this process, clients need to join a multicast group. When a message is sent, its destination address indicates that it is a multicast message. The multicast groups are dynamic with clients entering and leaving the group at any time.

Multicast is the old IPv4 CLASS D space and uses addresses 224.0.0.0 through 239.255.255.255. The IPv4 Multicast Address Space Registry lists multicast address assignments and is found at http://www.iana.org/assignments/multicast-addresses/multicast-addresses.xml. The Host Extensions for IP Multicasting document is found at http://tools.ietf.org/html/rfc1112. It defines the implementation requirements to support multicasting.

The UDP multicast server

The server application is declared next. This server is a time server that will broadcast the current data and time every second. This is a good...