How to
find IP address of local host from Java program
Java networking API provides method to find IP address of localhost from
Java program by using java.net. InetAddress class. It’s rare when you need IP
address for localhost in Java program. Mostly I used Unix
command to find IP address of localhost. For all practical purpose where
program doesn’t need IP address but you need to troubleshoot any networking
issues, Use DOS or windows command or Use Linux commands. Recently one of my
friend faced this question in a core
Java interview, where they are expecting Java developer with some socket
programming experience, But until you know or you have done it before its hard
to answer this fact based question, which motivates me to write this post. In
this Java tutorial we will see How to
find IP address of localhost from Java program. By the way it’s also good
to remember list
of Unix networking commands to troubleshoot any networking issues related to
Java application in Unix environment.
IP Address of localhost from Java program
As I said InetAddress from java.net package is
used to represent an IP address in Java. an IP address is a 32 or 128 bit
unsigned number used by IP protocol which is backbone of many popular protocols
like TCP and UDP. There are two kinds of IP address IPv4 and IPv6 and IP
address is associated with host which can be find by host name resolution
process. Hostname resolution is performed by combining local machine
configuration and network naming services such as the DNS(Domain name system) and NIS(Network
Information Service). InetAddress has method
to resolve hostname and IP address and vice versa. Here is a complete code example
of finding IP address from Java
program.
import java.net.UnknownHostException;
/**
* Simple Java program to find IP Address of localhost. This
program uses
* InetAddress from java.net
package to find IP address.
*
* @author Javin Paul
*/
public class
IPTest {
public static void
main(String args[]) throws
UnknownHostException {
InetAddress addr = InetAddress.getLocalHost();
//Getting IPAddress
of localhost - getHostAddress return IP Address
// in textual format
String ipAddress = addr.getHostAddress();
System.out.println("IP address of localhost from Java Program: "
+ ipAddress);
//Hostname
String hostname = addr.getHostName();
System.out.println("Name of hostname : " + hostname);
}
}
Output:
IP address of localhost from Java Program: 190.12.209.123
Name of hostname : PCLOND3433
That’s all on How to find IP address of localhost from Java. Its
nice tip to know but as I said java.net is not a common package like java.lang
or java.util. Best way to learn and remember networking concepts in Java is to
write some client server program which uses these essential classes.
Other Java Fundamentals tutorials from Javarevisited
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