[ACCEPTED]-How to get the ip of the computer on linux through Java?-ip-address

Do not forget about loopback addresses, which 3 are not visible outside. Here is a function 2 which extracts the first non-loopback IP(IPv4 1 or IPv6)

private static InetAddress getFirstNonLoopbackAddress(boolean preferIpv4, boolean preferIPv6) throws SocketException {
    Enumeration en = NetworkInterface.getNetworkInterfaces();
    while (en.hasMoreElements()) {
        NetworkInterface i = (NetworkInterface) en.nextElement();
        for (Enumeration en2 = i.getInetAddresses(); en2.hasMoreElements();) {
            InetAddress addr = (InetAddress) en2.nextElement();
            if (!addr.isLoopbackAddress()) {
                if (addr instanceof Inet4Address) {
                    if (preferIPv6) {
                        continue;
                    }
                    return addr;
                }
                if (addr instanceof Inet6Address) {
                    if (preferIpv4) {
                        continue;
                    }
                    return addr;
                }
            }
        }
    }
    return null;
}

From Java Tutorial

Why is InetAddress not a good solution? I don't 5 see anything in the docs about cross platform 4 compatibility?

This code will enumerate all 3 network interfaces and retrieve their information.

import java.io.*;
import java.net.*;
import java.util.*;
import static java.lang.System.out;

public class ListNets 
{
    public static void main(String args[]) throws SocketException {
        Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
        for (NetworkInterface netint : Collections.list(nets))
            displayInterfaceInformation(netint);
    }

    static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
        out.printf("Display name: %s\n", netint.getDisplayName());
        out.printf("Name: %s\n", netint.getName());
        Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
        for (InetAddress inetAddress : Collections.list(inetAddresses)) {
            out.printf("InetAddress: %s\n", inetAddress);
        }
        out.printf("\n");
     }
}  

The 2 following is sample output from the example 1 program:

Display name: bge0
Name: bge0
InetAddress: /fe80:0:0:0:203:baff:fef2:e99d%2
InetAddress: /121.153.225.59

Display name: lo0
Name: lo0
InetAddress: /0:0:0:0:0:0:0:1%1
InetAddress: /127.0.0.1

This code worked 4me:

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;


public class ShowIp {

    public static void main(String[] args) throws SocketException {
        NetworkInterface ni = NetworkInterface.getByName("eth0");
        Enumeration<InetAddress> inetAddresses =  ni.getInetAddresses();


        while(inetAddresses.hasMoreElements()) {
            InetAddress ia = inetAddresses.nextElement();
            if(!ia.isLinkLocalAddress()) {
                System.out.println("IP: " + ia.getHostAddress());
            }
        }
    }

}

0

It's not ok to just return the first non-loopback 3 interface as it might have been created 2 by some software like Parallels. It's a 1 better bet to try fishing for the eth0.

static private InetAddress getIPv4InetAddress() throws SocketException, UnknownHostException {

    String os = System.getProperty("os.name").toLowerCase();

    if(os.indexOf("nix") >= 0 || os.indexOf("nux") >= 0) {   
        NetworkInterface ni = NetworkInterface.getByName("eth0");

        Enumeration<InetAddress> ias = ni.getInetAddresses();

        InetAddress iaddress;
        do {
            iaddress = ias.nextElement();
        } while(!(iaddress instanceof Inet4Address));

        return iaddress;
    }

    return InetAddress.getLocalHost();  // for Windows and OS X it should work well
}

The simplest solution in my case was Socket.getLocalAddress(). I 4 had to open the Socket specifically for 3 that purpose, but with all the NetworkInterfaces 2 on my Ubuntu 10.04 machine it was the only 1 way to get the external IP address.

The best solution i've found is to run command 3 on linux / ubuntu machine. So I run this 2 command hostname -I | cut -d' ' -f1 using java.

note - second part of 1 method is just to collect the output.

public String getIP() throws IOException
{
    ProcessBuilder pb = new ProcessBuilder("bash", "-c", "hostname -I | cut -d' ' -f1");

    Process process = pb.start();
    InputStream inputStream = process.getInputStream();
    Scanner scanner = new Scanner(inputStream, StandardCharsets.UTF_8);

    StringBuilder outputString = new StringBuilder();
    while (scanner.hasNextLine())
    {
        synchronized (this)
        {
            String message = scanner.nextLine();
            outputString.append(message);
            outputString.append("\n");
            log(message);
        }
    }
    scanner.close();

    return outputString.toString().trim();
}