Hi, A Java networking problem has arisen very recently on one of our servers, an Opeteron with Scientific Linux 5.5, running the distro Java without problems--until a week or so ago. The effect is that all Java apps have become unable to do DNS host name resolution, and throw an UnknownHostException. However nothing seems otherwise amiss with networking on this machine. All non-Java programs resolve outside host names fine. I wrote a small test program, attached. It works fine on other machines here. Fails on the server, with an IP address. But if I give it a valid IP number, or the name of the server itself, it succeeds. I have done security updates fairly regularly; this may have something to do with the problem, but I really don't know for sure. Also tried: * Cut the hosts file down to the bare minimum, and also the resolv.conf file and re-started networking. No improvement. * Logged in as various users. All show the same problem. * Cut down and exported all related environment variables to bare minimum (JAVA_HOME, PATH, *LIBRARY_PATH, etc), No effect. * Reversed the updates from last week, and re-booted with the previous kernel. No improvement. * Fiddled with various Java system properties, as in http://download.oracle.com/javase/6/docs/technotes/guides/net/properties.html Nothing seemed to help. * Installed a Java 1.5, built the test program with it, ran the test program under that. It failed just like the distro version. Any ideas? ========================================================= To run the attached test javac nettest.java java nettest <hostname> <optional-port-number> -- | - - - - - - - - - - - - - - - - - - - - - - - - - | Steve White +49(331)7499-202 | E-Science Zi. 27 Villa Turbulenz | - - - - - - - - - - - - - - - - - - - - - - - - - | Astrophysikalisches Institut Potsdam (AIP) | An der Sternwarte 16, D-14482 Potsdam | | Vorstand: Prof. Dr. Matthias Steinmetz, Peter A. Stolz | | Stiftung privaten Rechts, Stiftungsverzeichnis Brandenburg: III/7-71-026 | - - - - - - - - - - - - - - - - - - - - - - - - -