(자바) InetAddress 클래스

InetAddress 클래스

통신 프로그램은 사실 인터넷이나 통신 규격이 요구하는 프로토콜을 만족시키는 데이터를 만드는 작업이다.

InetAddress 클래스는 인터넷 도메인이나 호스트를 IP주소로 전환하는 기능을 한다.

InetAddress클래스 특징

   - 객체를 생성하면 수정할 수 없다.

   - InetAddress 클래스는 일반적으로 IPv4 주소를 사용한다.

[IP주소 반환 받는 예제]

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class StringExample {
    public static void main(String args[]){
        InetAddress thisComputer = null;  

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));  
        System.out.println("Enter names and IP address. Enter \"exit\" to quit.");
        try{
            while(true){
                String host = in.readLine(); 
                
                if(host.equalsIgnoreCase("exit") ||
                        host.equalsIgnoreCase("quit")){
                    break;
                }

                try{
                    thisComputer = InetAddress.getByName(host);

                    System.out.println(thisComputer.getHostAddress());

                    if(thisComputer.isReachable(2000)){
                        System.out.printf("%s is reachable \n",thisComputer.getHostName());
                    }else{
                        System.out.printf("%s is unreachable \n",thisComputer.getHostName());
                    }
                }catch(UnknownHostException e){
                    System.out.println("Connot find host " + host);
                }
            }
        }catch(IOException e){
            System.err.println(e);
        }
    }
}

[결과]

Enter names and IP address. Enter "exit" to quit.
    www.google.com
    172.217.161.196
    www.google.com is unreachable
    127.0.0.1
    127.0.0.1
    localhost is reachable
    quit

    Process finished with exit code 0

---

[IP주소를 모두 받아오는 예제]

import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class StringExample {
    public static void main(String args[]){
        InetAddress address[] = null;
        String temp = "www.naver.com";

        try{
            address = Inet4Address.getAllByName(temp);
            for(InetAddress each: address){
                System.out.println("Name : " + each.getHostName());
                System.out.println("Addr : " + each.getHostAddress());
                System.out.println("Canonical : " + each.getCanonicalHostName());
            }

        }catch(UnknownHostException e){
            System.out.println("Name : " + args[0]);
        }
    }
}

[결과]

Name : www.naver.com
        Addr : 125.209.222.141
        Canonical : 125.209.222.141
        Name : www.naver.com
        Addr : 210.89.164.90
        Canonical : 210.89.164.90