How to get a list of IP connected in same network (subnet) using Java

Question

How do I get list of IP addresses for devices connected to my same subnet using Java?

Answer 1

this should work when the hosts on your network react to ICMP packages (ping) (>JDK 5):

public void checkHosts(String subnet){    int timeout=1000;    for (int i=1;i<255;i++){        String host=subnet + "." + i;        if (InetAddress.getByName(host).isReachable(timeout)){            System.out.println(host + " is reachable");        }    } } 

invoke the method for a subnet (192.168.0.1-254) like this:

checkHosts("192.168.0"); 

didnt test it but should work kinda like this. Obviously this only checks the 254 hosts in the last byte of the ip address...

check:

http://download-llnw.oracle.com/javase/6/docs/api/java/net/InetAddress.html#isReachable%28int%29 http://blog.taragana.com/index.php/archive/how-to-do-icmp-ping-in-java-jdk-15-and-above/

hope that helped

Answer 2

To list the hosts connected in a LAN you will need to ping all the available IP addresses on the subnet. But a ping message could be restricted by firewall thus safer way could be open a socket to each IP address in the LAN's IP address range.