I am having massive difficulties getting our application to talk to
our oracle database. We've (probably unwisely) upgraded the OS to RH9,
the database to Oracle 9i and the JDK to 1.3.1 (from RH7, 8i and 1.2).

The problem is that when I try to connect via JDBC in a jsp, it hangs
for a long time and comes back with "ServletException: Io exception:
the Network Adaptor could not make the connection." This seems to be a
common problem, but I have worked extensively on this, and have tried
all the posted remedies I can find: connect URL is verifiably correct,
database/listener running, path, networking, different connect
methods, etc.

At a low level, what happens is that the listener establishes the
connection, but never recieves a reply back, and I can't determine
whether oracle is failing (no trace/log seems to support it) or if
JDBC is failing. Since all I get is "Connection failed" in a single
method call, I'm not sure how to diagnose that.

Has anybody seen this before?