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Get the workstation name/ipTag(s): Networking


public class NetInfo {
 public static void main(String[] args) {
    new NetInfo().say();
    }

 public void say() {
   try {
   java.net.InetAddress i = java.net.InetAddress.getLocalHost();
   System.out.println(i);                  // name and IP address
   System.out.println(i.getHostName());    // name
   System.out.println(i.getHostAddress()); // IP address only
   }
   catch(Exception e){e.printStackTrace();}
 }
}
The output 
> java NetInfo
realone/209.142.72.112
realone
209.142.72.112

To list all the interfaces available on a workstation :
[JDK1.4] 

import java.net.*;
import java.util.*;
import java.io.*;
import java.nio.*;

public class IPAdress {
 public void  getInterfaces (){
      try {
         Enumeration e = NetworkInterface.getNetworkInterfaces();

         while(e.hasMoreElements()) {
            NetworkInterface ni = (NetworkInterface) e.nextElement();
            System.out.println("Net interface: "+ni.getName());

            Enumeration e2 = ni.getInetAddresses();

            while (e2.hasMoreElements()){
               InetAddress ip = (InetAddress) e2.nextElement();
               System.out.println("IP address: "+ ip.toString());
            }
         }
      }
      catch (Exception e) {
         e.printStackTrace();
      }
   }

   public static void main(String[] args) {
    IPAdress ip = new IPAdress();
    ip.getInterfaces();
   }
}
The output 
> java IPAdress
Net interface: lo
IP address: /127.0.0.1
Net interface: eth0
IP address: /194.168.0.1
Net interface: eth1
IP address: /164.254.147.20
Net interface: ppp0
IP address: /64.68.115.69
Windows

A "low-tech" way to get the computer name (can be useful if there is no network card) is to use the environment variable COMPUTERNAME (at least on modern Windows installation).

[JDK1.4 or less] Pass it to your JVM as java -Dcomputername="%COMPUTERNAME%" ... and then get the value with System.getProperty("computername")

[JDK1.5 or more] You can extract environment variable directly with System.getenv("COMPUTERNAME")

To get the IP of a client from the server side, see this HowTo.
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