[smokeping-users] Re: Another suggestion...

Hal Burgiss hal at foobox.net
Mon Jan 28 23:26:28 MET 2002

On Mon, Jan 28, 2002 at 05:04:03PM -0500, Paul C. Williamson wrote:
> What about pinging a specific port?  Although Tobi's idea 
> sounds way cooler.  I may look at that after I get this Cisco 
> thing working...

Well, you just can't do that with ICMP. There are other ways of doing
it. Something like nc, which just tries to open a port. And then there
is a hacker tool called hping, which can do tcp and udp pings just
like ping handles ICMP. But this plays havoc with my firewall since it
just sends a stream of SYNs (or whatever flag you set), and leaves the
connection open until it timeouts. Note to cr|hacker: please fix :)

The way I'd see testing a server is the time to get a valid response.
Say a web server, open connection, time to get an HTTP 200 response
or whatever, close connection. My perl is not so good, but I've played
with this some, and one hurdle I couldn't get past, is that IO::Socket
does not seem to ever time out. So if the server opens connection, but
does not conclude it, the connection just sits there. There probably
is a better module, but I never dug too deep into it.

Tobi, wouldn't getting SYN and ACK level data require putting
interface in promiscuous mode? I guess there is a perl sniffer ...
Hal Burgiss

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