I had several problems with informix SE on linux redhat 5.1.
It seems that many problems can be solved by using the fully qualified
name of your machine.
Before I couldn't use unnamed pipes. I allways got #25591. After I putted
the fully qualified name in the sqlhost file. (You get the name with
unmane -n), unnamed pipes worked.
Also when trying to use the JDBC drivers, it seemed that not much would
work. Trying several things, I saw with netstat -a that he tried to set up
a connection never made it to ESTABLISHED.
Trying to use the fully qualified name in the JDBC connection url in stead
of ip adress, it suddenly worked.
So although in the documentation of informix, the use of ip adress or
hostname stays the same, it seems that in reallity on some systems it only
works with the fully qualified name.
I don't says it's a mistake of informix. It's possible it's a kind of
misconfiguration of nameserver or some thing else.
But because lot's of people suffer this problem I found it a good idea to
post this message.