Today I tried to install Oracle AD4J on a Linux server that I have at home. The installation procedure is really simple and fully described here. Unfortunately, when I tried to access the console for the first time (that access is one of the installation steps), the HTTP server returned an internal server error (500). In the mod_jserv.log logfile I found the following error messages:
[13/02/2009 10:06:38:079] (EMERGENCY) ajp12: can not connect to host 127.0.0.1:3501 [13/02/2009 10:06:38:181] (EMERGENCY) ajp12: connection fail [13/02/2009 10:06:38:181] (ERROR) an error returned handling request via protocol "ajpv12"
Mhmm… a listener should be available on port 3501. But, no such listener was available on my system (note that port 3500 is used for the HTTP listener):
oracle@helicon:/u00/app/oracle/product/ad4j/ [rdbms11107] netstat -l --numeric-ports | grep 350[01] tcp 0 0 *:3500 *:* LISTEN
A quick search in Metalink revealed that at least another person has hit the same issue few days ago (see bug# 8235076). Since OSS is still working on it, I’ll wait to see what the findings are. In the mean time, I was able to successfully install it on my Windows laptop.
Anyway, if somebody of you managed to successfully install AD4J on Linux, please, let me know!
ADDENDA (February 16th, 2009): Because of the comments of Charles and Michael I spent a bit more time looking at the problem. In fact, the first time I stopped immediately after seeing the bug in Metalink… I was lazy 
. Hey, I try to optimize my worktime as well. Anyway, both suggested to manually start jserv. When I tried to do so, I received an error (at last). Based on it the problem was self explanatory! The java environment was causing the problem… In fact, with the default installation of CentOS 4.4 only the package java-1.4.2-gcj-compat was installed. After downloading and installing the most recent version of HotSpot (build 1.6.0_12-b04) the problem was solved.