What is the quickest way to detect an unreachable host in Java?

Question

I would like the fastest and most accurate function boolean isReachable(String host, int port) that passes the following JUnit tests under the conditions below. Tim

Answer 1

My most recent solution depends using a TimedSocket (source code) with 3000ms timeout while performing a connect.

Timings:

• 1406ms : testLocalHost()
• 5280ms : testLAN()

Can't even get these to work properly:

• testNoDNS()
• testHaveDNS()