Java menyediakan API jaringan yang kuat melalui paket java.net. Dengan memahami dasar Java Network, kamu bisa membuat:

• Aplikasi client-server

• Program yang berkomunikasi melalui TCP atau UDP

• Aplikasi yang mengakses web atau API

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Java Network Dasar

1. Paket java.net

Paket ini berisi kelas dan interface untuk komunikasi jaringan:

Kelas / Interface	Fungsi
InetAddress	Menyimpan alamat IP dan nama host
Socket	Membuat koneksi TCP client
ServerSocket	Membuat server TCP untuk mendengarkan koneksi
DatagramSocket	Socket UDP
DatagramPacket	Paket data untuk komunikasi UDP
URL	Mengakses resource web
HttpURLConnection	Membuat request HTTP/HTTPS

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2. InetAddress

Digunakan untuk mengetahui alamat IP lokal atau remote.

Contoh:

import java.net.InetAddress;

public class InetAddressExample {
    public static void main(String[] args) throws Exception {
        InetAddress ip = InetAddress.getByName("www.google.com");
        System.out.println("Host Name: " + ip.getHostName());
        System.out.println("IP Address: " + ip.getHostAddress());
    }
}

• getByName() → mendapatkan IP dari hostname

• getHostName() → nama host

• getHostAddress() → alamat IP

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3. Socket TCP (Client)

Client TCP menghubungi server melalui IP dan port.

Contoh:

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

public class TCPClient {
    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("localhost", 5000);
        DataOutputStream out = new DataOutputStream(socket.getOutputStream());
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        out.writeUTF("Hello Server");
        System.out.println("Server says: " + in.readLine());

        socket.close();
    }
}

• Socket → membuat koneksi ke server

• getOutputStream() → mengirim data

• getInputStream() → menerima data

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4. Server TCP

Server TCP mendengarkan koneksi client pada port tertentu.

Contoh:

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

public class TCPServer {
    public static void main(String[] args) throws Exception {
        ServerSocket server = new ServerSocket(5000);
        System.out.println("Server listening on port 5000");

        Socket client = server.accept();
        BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
        DataOutputStream out = new DataOutputStream(client.getOutputStream());

        String message = in.readLine();
        System.out.println("Client says: " + message);

        out.writeUTF("Hello Client");

        client.close();
        server.close();
    }
}

• ServerSocket.accept() → menunggu client terhubung

• Setelah client terhubung → dapat mengirim dan menerima data

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5. UDP Datagram

UDP digunakan untuk komunikasi cepat tanpa koneksi.

Contoh Client UDP:

import java.net.*;

public class UDPClient {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket();
        String msg = "Hello UDP Server";
        InetAddress address = InetAddress.getByName("localhost");

        DatagramPacket packet = new DatagramPacket(msg.getBytes(), msg.length(), address, 5000);
        socket.send(packet);
        socket.close();
    }
}

Contoh Server UDP:

import java.net.*;

public class UDPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(5000);
        byte[] buffer = new byte[1024];

        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
        socket.receive(packet);

        String received = new String(packet.getData(), 0, packet.getLength());
        System.out.println("Client says: " + received);

        socket.close();
    }
}

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6. HTTP Request Sederhana

Java dapat mengakses website atau API menggunakan HttpURLConnection.

Contoh:

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

public class HttpExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://www.haikalcctvid.org");
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");

        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println(inputLine);
        }
        in.close();
    }
}

• URL → alamat resource

• HttpURLConnection → metode request (GET, POST)

• InputStream → membaca response dari server

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Kesimpulan

Java Network Dasar meliputi:

• InetAddress → informasi IP/host

• Socket & ServerSocket → komunikasi TCP

• DatagramSocket & DatagramPacket → komunikasi UDP

• URL & HttpURLConnection → akses web dan API

Dengan memahami dasar ini, kamu bisa mulai membuat aplikasi jaringan sederhana, seperti chat client-server, monitoring server, atau akses API.

Untuk tutorial Java Network lanjutan, termasuk multithreaded server dan HTTP/HTTPS client, kunjungi 🌐 www.haikalcctvid.org.

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