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  • Sasha Robbins thinks this is interesting:

We will use the sock program [SOCK] to generate some UDP datagrams that we can watch with tcpdump. In the first example, we are running a server on the discard port (9) on the destination machine. In the second example, we have disabled the server, and the client is informed of this fact as illustrated here. Very few UDP-based services are made available in typical machine configurations because of security concerns, so the second part of the example is not unusual.


Cover of TCP/IP Illustrated, Volume 1: The Protocols