Test for server availability

[pwills]

Is this possible?
I'd like the page myserver/redirect.asp to test whether server1 is responding. If it is, then it redirects the user to server1, otherwise server2.
In English, redirect.asp would be something like:

if (server1/up.txt <> 'yes')
if (server2/up.txt <> 'yes')
write('sorry, both servers are down')
else
redirect_to (server2)
endif
else
redirect_to (server1)
endif