Problem with isReachable in InetAddress class

Question

As an assignment I have to find all the alive computers on a LAN. For which I am using isReachable function of InetAddress class. But problem is

Answer 1

Here are some details on why isReachable() might not always work as expected

1. http://bordet.blogspot.com/2006/07/icmp-and-inetaddressisreachable.html
2. http://www.coderanch.com/t/206934/sockets/java/InetAdress-isReachable-Ping-Permissions

The correct way for you is to use the ICMP protocol. This is what ping uses internatlly, I believe. Here is an example that get you started.