How to check if an IP address is the local host on a multi-homed system?

Question

For a machine with multiple NIC cards, is there a convenient method in Java that tells whether a given IP address is the current machine or not. e.g.

boolean IsThisMyIpAddress("192.168.220.25"); 

Answer 1

If you are looking for any IP address that is valid for the local host then you must check for special local host (e.g. 127.0.0.1) addresses as well as the ones assigned to any interfaces. For instance...

public static boolean isThisMyIpAddress(InetAddress addr) {     // Check if the address is a valid special local or loop back     if (addr.isAnyLocalAddress() || addr.isLoopbackAddress())         return true;      // Check if the address is defined on any interface     try {         return NetworkInterface.getByInetAddress(addr) != null;     } catch (SocketException e) {         return false;     } } 

With a string, indicating the port, call this with:

boolean isMyDesiredIp = false; try {     isMyDesiredIp = isThisMyIpAddress(InetAddress.getByName("192.168.220.25")); //"localhost" for localhost } catch(UnknownHostException unknownHost) {     unknownHost.printStackTrace(); }