How to check if an IP address is from a particular network/netmask in Java?

Question

I need to determine if given IP address is from some special network in order to authenticate automatically.

Answer 1

Apache Commons Net has org.apache.commons.net.util.SubnetUtils that appears to satisfy your needs. It looks like you do something like this:

SubnetInfo subnet = (new SubnetUtils("10.10.10.0", "255.255.255.128")).getInfo();
boolean test = subnet.isInRange("10.10.10.10");

Note, as carson points out, that Apache Commons Net has a bug that prevents it from giving the correct answer in some cases. Carson suggests using the SVN version to avoid this bug.