Does anyone know how you get the local network address of a machine in Java? (eg. 192.168.0.1, not the loopback ip).

Thanks

 

 

import java.net.*;
import java.io.*;
 
 
public class URLReader {
 
 
  public static void main(String[] args) throws Exception {
 
	
	System.out.println(getName());
	    
    }
    
  static String getName() throws Exception {
	InetAddress inet = 	InetAddress.getLocalHost();
	
	return inet.getHostAddress();
 
	}    
    
}
 

 

 

Thanks, but that returns 127.0.0.1 for me.

 

 

Try this:

    public static InetAddress[] localHostAddresses()
        throws UnknownHostException
    {
            InetAddress localhost = InetAddress.getLocalHost();
            InetAddress addresses[] = InetAddress.getAllByName(localhost.getHostName());
            return addresses;
    }

There is also another in www.javaalmanac.com in the java.net category.

 

 

Thanks, but that just returns 127.0.0.1 for me too.

The ones in the Java Almanac seem to be the same, they just used byte arrays instead?

 

 

It seems mapping the hostname for my computer in /etc/hosts to 192.168.x.x instead of 127.0.0.1 solves this.

 

 

There's a pretty 'dirty' way to do this assuming you have a computer that is ALWAYS on the network. Let's pretend this computer is named 'bob' on the network. You could have 'bob' be running this server:

import java.io.*;
import java.net.*;
public class Bob {
	public Bob() throws IOException {
		ServerSocket server = new ServerSocket(6000);
		Socket client;
		PrintStream out;
		while (true) {
			client = server.accept();
			out = new PrintStream(client.getOutputStream());
			out.print(client.getInetAddress().getHostAddress());
			out.close();
			client.close();
		}
	}
	public static void main(String args[]) {
		try {
			new Bob();
		}
		catch (IOException e) {
			e.printStackTrace();
		}
	}
}

And then on your side, you could use the getIP() method demonstrated in this program:

import java.io.*;
import java.net.*;
public class Example {
	public Example() {
		String address = "N/A";
		try {
			address = getIP();
		}
		catch (IOException e) {
			address = "N/A";
			e.printStackTrace();
		}
		System.out.println("Address: "+address);
	}
	protected String getIP() throws IOException {
		Socket s = new Socket("bob",6000);
		BufferedReader b = new BufferedReader(new InputStreamReader(s.getInputStream()));
		return b.readLine();
	}
	public static void main(String args[]) {
		new Example();
	}
}

This will work ONLY if 'bob' is a DIFFERENT computer than the one thats running the getIP(). If it's run on the same machine, getIP() will obviously return 127.0.01.

 

 

Well, it looks like you were running that code on a machine without Internet connection. But if you were on windows machine and connected, then the sample code given by andresurbina should work like charm for you.

All the best.