Important notes re IPv6

The AstroGrid server-side components currently require Java 1.4; various libraries they depend on are not currently compatible with Java 1.5.

At least some versions of Java 1.4 are incompatible with the IPv6 networking protocol, leading to socket errors when Java attempts to establish network connections.

A symptom of this problem is when tomcat's "startup.sh" script will start successfully, but the "shutdown.sh" script will fail to shut tomcat down again.

IPb6 is enabled by default in Fedora Core 4, and in recent kernel updates (2.6.12) to Fedora Core 3.

Java can be told to use IPv4 rather than IPv6, by setting the property "java.net.preferIPv4Stack" to "true". For example, you can set this property in the JAVA_OPTS environment variable of your tomcat user, and java will then pick it up when starting tomcat. A sample setting might be:

JAVA_OPTS=-server -Xmx1024M -XX:+UseAdaptiveSizePolicy -Djava.net.preferIPv4Stack=true

Please keep us informed if you come across other IPv6-related issues or fixes.

-- KonaAndrews - 19 Jul 2005

The latest kernel updates for FedoraCore^? 3 (2.6.12-1.1372_FC3) can cause IPV6 problems with Java JDK-1.4.2.

Amongst other things, maven fails to download jars from remote repositories. The symptoms are

java.net.SocketException: Invalid argument or cannot assign requested address

The fix is to add -Djava.net.preferIPv4Stack=true to the MAVEN_OPTS environment variable (the maven shell scripts don't read the JAVA_OPTS used by Tomcat).

The easiest way to do this is to add the following to a file called .mavenrc in your home directory.

if [ -z "$MAVEN_OPTS" ] ; then
  MAVEN_OPTS="-Djava.net.preferIPv4Stack=true"
fi