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Programmatic Access to Network Parameters
Retrieving Network Interfaces
The
NetworkInterface class has no public constructor. Therefore,
you cannot just create a new instance of this class with the
new
operator. Instead, the following static methods are
available so that you can retrieve the interface details from the system:
getByInetAddress(),
getByName(), and
getNetworkInterfaces(). The first two methods are
used when you already know the IP address or the name of the
particular interface. The third method,
getNetworkInterfaces()
returns the complete list of interfaces on the machine.
Network interfaces can be hierarchically organized.
The NetworkInterface class includes two methods,
getParent() and getSubInterfaces(), that are
pertinent to
a network interface hierarchy. The getParent() method returns
the parent NetworkInterface of an interface. If a network
interface is a subinterface, getParent() returns a non-null
value. The getSubInterfaces() method returns all the
subinterfaces of a network interface.
The following example program lists the name of all the network interfaces and
subinterfaces (if any exist) on a machine.
import java.io.*;
import java.net.*;
import java.util.*;
import static java.lang.System.out;
public class ListNIFs
{
public static void main(String args[]) throws SocketException {
Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
for (NetworkInterface netIf : Collections.list(nets)) {
out.printf("Display name: %s\n", netIf.getDisplayName());
out.printf("Name: %s\n", netIf.getName());
displaySubInterfaces(netIf);
out.printf("\n");
}
}
static void displaySubInterfaces(NetworkInterface netIf) throws SocketException {
Enumeration<NetworkInterface> subIfs = netIf.getSubInterfaces();
for (NetworkInterface subIf : Collections.list(subIfs)) {
out.printf("\tSub Interface Display name: %s\n", subIf.getDisplayName());
out.printf("\tSub Interface Name: %s\n", subIf.getName());
}
}
}
The following is sample output from the example program:
Display name: bge0
Name: bge0
Sub Interface Display name: bge0:3
Sub Interface Name: bge0:3
Sub Interface Display name: bge0:2
Sub Interface Name: bge0:2
Sub Interface Display name: bge0:1
Sub Interface Name: bge0:1
Display name: lo0
Name: lo0
