javasocket白板程序

Java Socket是一种在Java编程语言中提供的API，用于实现网络通信。白板程序是指可以在多个用户之间共享画板，实现实时绘图的应用程序。

下面是一个简单的Java Socket白板程序的示例：

1. 服务器端代码：

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

public class WhiteboardServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 4444.");
            System.exit(1);
        }
        Socket clientSocket = null;
        try {
            System.out.println("Waiting for client...");
            clientSocket = serverSocket.accept();
            System.out.println("Client connected.");
        } catch (IOException e) {
            System.err.println("Accept failed.");
            System.exit(1);
        }
        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println("Client: " + inputLine);
            out.println(inputLine);
            if (inputLine.equals("Bye.")) {
                break;
            }
        }
        out.close();
        in.close();
        clientSocket.close();
        serverSocket.close();
    }
}

2. 客户端代码：

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

public class WhiteboardClient {
    public static void main(String[] args) throws IOException {
        Socket echoSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
        try {
            echoSocket = new Socket("localhost", 4444);
            out = new PrintWriter(echoSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: localhost.");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for the connection to: localhost.");
            System.exit(1);
        }
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        String userInput;
        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput);
            System.out.println("Server: " + in.readLine());
            if (userInput.equals("Bye.")) {
                break;
            }
        }
        out.close();
        in.close();
        stdIn.close();
        echoSocket.close();
    }
}

这个白板程序的实现方式是：客户端向服务器发送消息，服务器原封不动地将消息返回给客户端。在实际应用中，可以将消息解析为绘图指令，并在客户端的画板上进行绘制。