Java Program to Determine Hostname from IP Address

IP Address stands for internet protocol address. It is an identifying number that is associated with a specific computer or computer network. IP addresses are usually written and displayed in human-readable notation such as 192.168.1.35 in IPv4(32-bit IP address). When connected to the internet, the IP address allows the computers to send and receive information. Every site has its own host link to their own IP Address which helps to send the request by the user to the HTTP traffic and helps to collect the information which the users want This is how an IP address is necessary for every host.

There are many ways to get the IP Address of a particular host. So the method which helps to get the IP address for any Host is getHostAddress() of InetAddress class.

Syntax:

public String getHostAddress() 

Returns: It returns the raw IP address in a string format.

Note: It is easy to find the IP Address from a Hostname. But due to security reasons, it is difficult to get the Host Name from the IP address because all IP addresses are secured. 

The following methods are used to get the Host Name.

• getHostName(): This function retrieves the standard hostname for the local computer.
• getHostByName(): This function retrieves host information corresponding to a hostname from a host database.

Example: Obtaining the IP address from the given host

Java

// Java program to obtain IP Address
// from a given host

import java.io.*;
import java.util.*;
import java.net.*;
class GFG {
    public static void main(String[] args)
    {
          // Host
        String host = "www.geeksforgeeks.org";

        // Using try Logic So that if there is an error then
        // easily get the error
        try {

            // calling the function which gives the IP
            // Address from the given host
            InetAddress[] iaddress
                = InetAddress.getAllByName(host);

            for (InetAddress ipaddresses : iaddress) {
                System.out.println(ipaddresses.toString());
            }
        }
        catch (UnknownHostException e) {
            System.out.println(e);
        }
    }
}

Example: Obtaining the Hostname from the Given IP address. All the Server and IP are Secured for a security reason So Hostname directly from the IP address cannot be found. But the Method is similar to found any Hostname from the unsecured IP address.

Java

// Java program to get Host name
// from an ipaddress

import java.io.*;
import java.net.*;
class GFG {
    public static void main(String[] args)
    {
        try {
            // IP Address
            InetAddress addr
                = InetAddress.getByName("23.229.203.68");

            // Host name
            System.out.println("Host name is: "
                               + addr.getHostName());

            // Host Address
            System.out.println("Ip address is: "
                               + addr.getHostAddress());
        }
        catch (UnknownHostException e) {
            System.out.println(e);
        }
    }
}

Output

Host name is: 23.229.203.68
Ip address is: 23.229.203.68