How to troubleshoot authentication failure?

[Kynn Jones <kynnjo@xxxxxxxxx>]

I have two Linux servers that are pretty similar to each other, and both are running PostgreSQL servers, but in one server a certain Perl script succeeds in connecting to the localhost server whereas in the other one the same script fails.  The error on the second server is of the form "fe_sendauth: no password supplied".

I have verified all the possible reasons that I can think of for why this script succeeds on one server but fails on the other.  In all these respects the two set ups are absolutely identical: same pg_hba.conf files, same script parameters, same versions of Postgres, same everything.

I have run out of ideas!

How can I troubleshoot this further?  Is there some way to have Postgres dump excruciatingly thorough details about every single step of the authentication sequence?

Any other suggestions would be greatly appreciated.

Thanks!

k