Socket編程在Java中的應用

Socket編程是一種通信協議，用於在計算機網路中進行通信。Java提供了很多Socket類庫，允許我們使用Socket進行網路通信。

一、Socket基礎概念

1、Socket是什麼？

Socket是一個端點，用於兩個不同的進程之間的通信。

2、Socket如何工作？

Socket工作方式分為兩種：客戶端和伺服器端。

客戶端向伺服器端發送請求，伺服器端接收請求並向客戶端發送響應。這種工作方式稱為Client-Server模式。

二、Socket編程的運用

1、基於TCP協議的Socket編程示例

// 伺服器端
import java.net.*;
import java.io.*;

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(6666);
        System.out.println("Server started.");

        while (true) {
            Socket socket = null;
            try {
                socket = serverSocket.accept();
                System.out.println("New client connected: " + socket);

                DataInputStream in = new DataInputStream(socket.getInputStream());
                DataOutputStream out = new DataOutputStream(socket.getOutputStream());

                String message = "";
                while (!message.equals("exit")) {
                    message = in.readUTF();
                    System.out.println("Message received from client: " + message);

                    out.writeUTF("Server received the message: " + message);
                }
            } catch (Exception e) {
                socket.close();
                e.printStackTrace();
            }
        }
    }
}

// 客戶端
import java.net.*;
import java.io.*;

public class Client {
    public static void main(String[] args) throws IOException {
        try {
            Socket socket = new Socket("localhost", 6666);
            System.out.println("Connected to server.");

            DataInputStream in = new DataInputStream(socket.getInputStream());
            DataOutputStream out = new DataOutputStream(socket.getOutputStream());

            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            String message = "";
            while (!message.equals("exit")) {
                System.out.println("Enter a message: ");
                message = reader.readLine();

                out.writeUTF(message);
                String receivedMessage = in.readUTF();
                System.out.println("Message received from server: " + receivedMessage);
            }

            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2、基於UDP協議的Socket編程示例

// 伺服器端
import java.io.*;
import java.net.*;

public class Server {
    public static void main(String[] args) throws IOException{
        DatagramSocket serverSocket = new DatagramSocket(6565);
        System.out.println("Server started.");
        
        byte[] receiveData = new byte[1024];
        byte[] sendData = new byte[1024];
        
        while(true){
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            serverSocket.receive(receivePacket);
            
            String message = new String(receivePacket.getData());
            System.out.println("Message received from client: " + message);
            
            InetAddress IPAddress = receivePacket.getAddress();
            int port = receivePacket.getPort();
            
            String returnMessage = "Server received the message: " + message;
            sendData = returnMessage.getBytes();
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
            
            serverSocket.send(sendPacket);
        }
    }
}

// 客戶端
import java.io.*;
import java.net.*;

public class Client {
    public static void main(String[] args) throws Exception{
        DatagramSocket clientSocket = new DatagramSocket();
        InetAddress IPAddress = InetAddress.getByName("localhost");

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        
        byte[] sendData = new byte[1024];
        byte[] receiveData = new byte[1024];
        
        String message = "";
        while(!message.equals("exit")){
            System.out.println("Enter a message:");
            message = reader.readLine();
            
            sendData = message.getBytes();
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 6565);
            
            clientSocket.send(sendPacket);
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            
            clientSocket.receive(receivePacket);
            String receivedMessage = new String(receivePacket.getData());
            System.out.println("Message received from server: " + receivedMessage);
        }
        
        clientSocket.close();
    }
}

三、Socket編程的注意事項

1、Socket編程需要關閉Socket資源，以免網路通信佔用過多資源。

2、在Socket編程過程中，需要注意數據的傳輸方式和數據的大小。

3、Socket編程需要考慮網路安全問題，防止惡意攻擊。

總之，Socket編程在Java中的應用非常廣泛，涉及到多種不同的領域，如Web開發、移動應用程序開發等。通過Socket編程，我們可以實現不同進程之間的通信，從而創造出更多有趣的應用場景。