Internet Addresses - Java Network Programming - page 109

that particular network interface. For example, this code fragment attempts to find the
primary Ethernet interface on a Unix system:
try {
NetworkInterface ni = NetworkInterface . getByName ( "eth0" );
if ( ni == null ) {
System . err . println ( "No such interface: eth0" );
}
} catch ( SocketException ex ) {
System . err . println ( "Could not list sockets." );
}
public static NetworkInterface getByInetAddress(InetAddress address) throws SocketException
The getByInetAddress() method returns a NetworkInterface object representing the
network interface bound to the specified IP address. If no network interface is bound
to that IP address on the local host, it returns null. If anything goes wrong, it throws a
SocketException . For example, this code fragment finds the network interface for the
local loopback address:
try {
InetAddress local = InetAddress . getByName ( "127.0.0.1" );
NetworkInterface ni = NetworkInterface . getByInetAddress ( local );
if ( ni == null ) {
System . err . println ( "That's weird. No local loopback address." );
}
} catch ( SocketException ex ) {
System . err . println ( "Could not list network interfaces." );
} catch ( UnknownHostException ex ) {
System . err . println ( "That's weird. Could not lookup 127.0.0.1." );
}
public static Enumeration getNetworkInterfaces() throws SocketException
The getNetworkInterfaces() method returns a java.util.Enumeration listing all the
network interfaces on the local host. Example 4-8 is a simple program to list all network
interfaces on the local host:
Example 4-8. A program that lists all the network interfaces
import java.net.* ;
import java.util.* ;
public class InterfaceLister {
public static void main ( String [] args ) throws SocketException {
Enumeration < NetworkInterface > interfaces = NetworkInterface . getNetwork
Interfaces ();
while ( interfaces . hasMoreElements ()) {
NetworkInterface ni = interfaces . nextElement ();
System . out . println ( ni );
}