Java Networking – inetAddress

In Java, InetAddress is a class that represents an IP address and provides methods to work with IP addresses and hostnames. It is part of the java.net package and is used in network programming for tasks such as resolving hostnames, retrieving IP addresses, and performing network-related operations. Here’s an overview of InetAddress in Java networking but before lets see Java.Net Package first.

Java.Net Package

The java.net package in Java provides classes and interfaces for network programming. It offers a wide range of functionalities to create networked applications, interact with network protocols, perform network operations, and handle communication over the network. Here’s an overview of some important classes and interfaces in the java.net package:

1. URL: The URL class represents a Uniform Resource Locator and provides methods to work with URLs. It allows you to create, parse, and manipulate URLs, and provides access to different components of a URL, such as the protocol, host, port, path, query parameters, and more.

2. URLConnection: The URLConnection class represents a connection to a resource specified by a URL. It provides methods to establish a connection, read data from the resource, write data to the resource, handle request properties, and access response headers.

3. InetAddress: The InetAddress class represents an IP address and provides methods to work with IP addresses and hostnames. It allows you to resolve hostnames to IP addresses and vice versa, obtain the IP address of the local machine, check reachability, and more.

4. Socket and ServerSocket: The Socket class represents a client-side endpoint of a connection, while the ServerSocket class represents a server-side endpoint. These classes are used for creating client-server applications and allow communication over TCP/IP. They provide methods to establish connections, send and receive data, handle timeouts, and manage socket options.

5. DatagramSocket and DatagramPacket: The DatagramSocket class is used for connectionless communication using the UDP (User Datagram Protocol). It allows sending and receiving datagram packets, which are small units of data. The DatagramPacket class encapsulates the data and addressing information for the packet.

6. SocketTimeoutException: This exception is thrown when a socket operation times out due to a specified timeout value. It is commonly used to handle situations where a socket connection or operation takes longer than expected.

7. URI: The URI class represents a Uniform Resource Identifier and provides methods to work with URIs. It allows you to create, parse, and manipulate URIs, and provides access to different components of a URI, such as the scheme, authority, path, query, and fragment.

8. URLDecoder and URLEncoder: These utility classes provide methods to decode and encode URL-encoded strings, respectively. They are useful for handling special characters and ensuring proper encoding of URLs.

These are just a few examples of the classes and interfaces provided by the java.net package. The package also includes classes for working with proxy servers, handling network interfaces, performing network-related operations (such as pinging), and more. The java.net package is an essential part of network programming in Java, enabling developers to build networked applications, interact with network protocols, and perform various network operations.

Here’s an overview of InetAddress in Java networking

IP Address Representation:

The InetAddress class represents an IP address, which can be either an IPv4 address (e.g., 192.0.2.1) or an IPv6 address (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). The InetAddress class provides methods to obtain the address in both textual and byte array formats.

Example

Resolving Hostnames:

The InetAddress class offers methods to resolve hostnames to IP addresses and vice versa. The getByName() method takes a hostname as input and returns an InetAddress object representing the IP address corresponding to that hostname. Conversely, the getHostName() method retrieves the hostname associated with an InetAddress object.

Lets check below example

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

public class getipofhost {
public static void main(String[] args)
throws Exception {
InetAddress ip = InetAddress.getByName("www.examradar.com");
System.out.println("IP:  "+ip);

  }

}

LocalHost:

The InetAddress class provides a static method called getLocalHost() that returns the InetAddress object representing the current machine’s IP address or hostname. This method is often used to determine the IP address or hostname of the local machine.

InetAddres : Method

Lets check below example

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

public class getipofhost {
public static void main(String[] args)
throws Exception {
  InetAddress ip = InetAddress.getLocalHost();
  System.out.println("LocalHost:  "+ip);
  }

}

InetAddres : Method

Let’s check below example:

 import java.io.*; import java.net.*; public class getipofhost { public static void main(String[] args) throws Exception { InetAddress ip = InetAddress.getByName(“192.168.225.32”); System.out.println(“HostName:  “+ip.getHostName()); } }

InetAddres : Method

Lets check below example:

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

public class getipofhost {

public static void main(String[] args)
throws Exception {
  InetAddress ip = InetAddress.getByName("www.examradar.com");
  System.out.println("HostAddress:  "+ip.getHostAddress());

  }

}

Other Methods of inetAddress

Multiple IP Addresses:

In some cases, a single hostname can be associated with multiple IP addresses. The getAllByName() method allows retrieving an array of InetAddress objects representing all the IP addresses associated with a given hostname.

Utility Methods:

The InetAddress class provides additional utility methods, such as isReachable() to check if a remote IP address is reachable, isLoopbackAddress() to determine if an IP address represents the loopback address (localhost), and isAnyLocalAddress() to check if an IP address represents any local address.

Example usage of InetAddress:

import java.net.InetAddress;
import java.net.UnknownHostException;

public class InetAddressExample {
    public static void main(String[] args) {
        try {
            // Resolving hostname to IP address
            InetAddress address = InetAddress.getByName("www.example.com");
            System.out.println("IP Address: " + address.getHostAddress());

            // Resolving IP address to hostname
            InetAddress address2 = InetAddress.getByName("192.0.2.1");
            System.out.println("Hostname: " + address2.getHostName());

            // Getting the IP address of the local machine
            InetAddress localAddress = InetAddress.getLocalHost();
            System.out.println("Local IP Address: " + localAddress.getHostAddress());
            System.out.println("Local Hostname: " + localAddress.getHostName());
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

The InetAddress class in Java provides a convenient way to work with IP addresses and hostnames in network programming. It allows developers to resolve hostnames, retrieve IP addresses, and perform other network-related tasks in their Java applications.