I have selected loopback (in capture options) to capture http traffic on my localhost server, but everytime I do and HTTP I only can see TCP.
1 Answer
Presumably that's because no process on the machine is sending UDP packets to another endpoint on the same machine. Try doing ping 127.0.0.1 while you're capturing on lo0 and see whether ICMP packets show up (they do, at least on my Mountain Lion machine).
