Why does InstallJava[] hang on my Mac running OS X 10.3.8?

This is caused by a problem in OS X 10.3.8. The MathLink library has a module that keeps track of the network interfaces and their associated IP numbers and hostnames. When this module configures itself, it determines the IP address assigned to an interface. From that IP address, it determines the hostname associated with the interface’s IP address. The library module uses two functions, gethostbyaddr() and gethostbyname() to verify the name associated with the IP number.

On a correctly functioning system, the gethostbyaddr() function should return the equivalent of “no DNS entry” for any network number in a private network subnet (one of the 192.168.x.x or 10.x.x.x, barring of course the case in which the administrator of the private subnet has assigned hostnames to the subnet hosts through the use of /etc/hosts). On an OS X 10.3.8 system, when you give gethostbyaddr() an IP number from a private subnet, the function returns a DNS entry with the hostname set to “localhost”. The actual value of the private subnet IP number doesn’t appear to matter, the function always returns “localhost”.

In addition, we also discovered that this problem doesn’t occur when tested from a standalone kernel because J/Link doesn’t make use of a TCP/IP link in this case. The front end must have already launched the kernel for J/Link to use a TCP/IP link.

Our developers notified Apple of this incorrect behavior. Shortly afterward, Apple fixed this problem in the 10.3.9 update of OS X. Please consider obtaining this update if you are experiencing hanging problems upon evaluation of InstallJava[] in Mathematica.

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