Java Getting My Ip Address

Java getting my IP address

The NetworkInterface class contains all the relevant methods, but be aware that there's no such thing as "my IP". A machine can have multiple interfaces and each interface can have multiple IPs.

You can list them all with this class but which interface and IP you choose from the list depends on what you exactly need to use this IP for.

(InetAddress.getLocalHost() doesn't consult your interfaces, it simply returns constant 127.0.0.1 (for IPv4))

Getting the IP address of the current machine using Java

import java.net.DatagramSocket;
import java.net.InetAddress;

try(final DatagramSocket socket = new DatagramSocket()){
  socket.connect(InetAddress.getByName("8.8.8.8"), 10002);
  ip = socket.getLocalAddress().getHostAddress();
}

This way works well when there are multiple network interfaces. It always returns the preferred outbound IP. The destination 8.8.8.8 is not needed to be reachable.

Connect on a UDP socket has the following effect: it sets the destination for Send/Recv, discards all packets from other addresses, and - which is what we use - transfers the socket into "connected" state, settings its appropriate fields. This includes checking the existence of the route to the destination according to the system's routing table and setting the local endpoint accordingly. The last part seems to be undocumented officially but it looks like an integral trait of Berkeley sockets API (a side effect of UDP "connected" state) that works reliably in both Windows and Linux across versions and distributions.

So, this method will give the local address that would be used to connect to the specified remote host. There is no real connection established, hence the specified remote ip can be unreachable.

Edit:

As @macomgil says, for MacOS you can do this:

Socket socket = new Socket();
socket.connect(new InetSocketAddress("google.com", 80));
System.out.println(socket.getLocalAddress());

How to get the IP address of a machine in Java

You can get the IP address of your machine using the following call:

Inet4Address.getLocalHost().getHostAddress();

The above is in the Java APIs, so you don't need any jar for that.

Java Getting IPv4 Address

You can check the type of the addr object to see if it's an Inet4Address or an Inet6Address instance.

For example:

String ip;
try {
    Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
    while (interfaces.hasMoreElements()) {
        NetworkInterface iface = interfaces.nextElement();
        // filters out 127.0.0.1 and inactive interfaces
        if (iface.isLoopback() || !iface.isUp())
            continue;

        Enumeration<InetAddress> addresses = iface.getInetAddresses();
        while(addresses.hasMoreElements()) {
            InetAddress addr = addresses.nextElement();

            // *EDIT*
            if (addr instanceof Inet6Address) continue;

            ip = addr.getHostAddress();
            System.out.println(iface.getDisplayName() + " " + ip);
        }
    }
} catch (SocketException e) {
    throw new RuntimeException(e);
}

how to get the ip address of the connected interface

this should do the trick:

import java.io.*;
import java.util.*;

public class ExecTest {
public static void main(String[] args) throws IOException {
    Process result = Runtime.getRuntime().exec("traceroute -m 1 www.amazon.com");

    BufferedReader output = new BufferedReader(new            InputStreamReader(result.getInputStream()));
    String thisLine = output.readLine();
    StringTokenizer st = new StringTokenizer(thisLine);
    st.nextToken();
    String gateway = st.nextToken();
    System.out.printf("The gateway is %s\n", gateway);
}
}

Courtesy of Chris Bunch from: How can I determine the IP of my router/gateway in Java?

Greets!

Getting the 'external' IP address in Java

I am not sure if you can grab that IP from code that runs on the local machine.

You can however build code that runs on a website, say in JSP, and then use something that returns the IP of where the request came from:

request.getRemoteAddr()

Or simply use already-existing services that do this, then parse the answer from the service to find out the IP.

Use a webservice like AWS and others

import java.net.*;
import java.io.*;

URL whatismyip = new URL("http://checkip.amazonaws.com");
BufferedReader in = new BufferedReader(new InputStreamReader(
                whatismyip.openStream()));

String ip = in.readLine(); //you get the IP as a String
System.out.println(ip);

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