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Taking Your network’s
A prescription for capturing data to diagnose and debug a networking problem.
I posted a question on a mailing list
recently about a networking problem
and was asked if I had a tcpdump. The
person who responded to my question—and to the whole list as well—
seemed to think my lack of networking
knowledge was some kind of affront to
him. His response was pretty much a
personal attack: If I couldn’t be bothered to do the most basic types of debugging on my own, then I shouldn’t
expect much help from the list. Aside
from the personal attack, what did he
mean by this?
how to debug a program during their
studies is small, the number who learn
how to debug a networking problem is
minuscule. I actually don’t know anyone who was ever directly taught how
to debug a networking problem.
Some people—the lucky ones—are
eventually led to the program you men-
tion, tcpdump, or its graphical equiva-
lent, wireshark, but I’ve never seen
anyone try to teach people to use these
tools. One of the nice things about
tcpdump and wireshark is that they’re
multi-platform, running on both Unix-
like operating systems and Windows.
In fact, writing a packet-capture pro-
gram is relatively easy, as long as the
operating system you’re working with
gives you the ability to tap into the net-
working code or driver at a low enough
level to sniff packets.