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Java.net.NetworkInterface: a road warrior''s friend. (Network Connectivity).

Article Excerpt
My laptop goes where I go. Some people like to read; I like to hack code. Just ask my wife--I took the laptop on vacation to the Cayman Islands. The problem I'm having is that I can never predict the state of my online connection. At home I'm wireless; at work, wired. In between, such as my 90-minute daily train commute, I'm neither. Don't get me started on the lousy connectivity from the beach. That downtime is a serious productivity killer, since all my Web-enabled code becomes unstable. There are many layers to a J2EE application these days and I don't control all of them, so I have no guarantee that my app will behave properly if a connection fails. Worst case scenarios--I might time out, hang, or crash altogether.

The thing is I can predict my downtimes. If I take my network card out, it's a safe bet I don't have a connection. Instead of tackling the rather large problem of detecting a good network connection, I took a different approach. I started researching whether I could tell my application that I definitely did not have a connection. If I could easily write something that says "If not connected, then don't try to perform Net-sensitive code," that would take care of the majority of my downtime. After some research I discovered that java.net. NetworkInterface, new in Java 1.4, does almost exactly what I need.

Guaranteeing that a machine is "online" is near impossible...