java如何使用socket

使用Socket进行Java网络通信

在Java中，Socket用于实现客户端与服务器之间的网络通信。以下是使用Socket进行通信的基本方法。

创建服务器端

服务器端通过ServerSocket监听指定端口，等待客户端连接。连接建立后，通过Socket进行通信。

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

public class Server {
    public static void main(String[] args) throws IOException {
        int port = 12345;
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("服务器启动，等待客户端连接...");

        Socket clientSocket = serverSocket.accept();
        System.out.println("客户端已连接");

        BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);

        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println("收到客户端消息: " + inputLine);
            out.println("服务器回复: " + inputLine);
        }

        in.close();
        out.close();
        clientSocket.close();
        serverSocket.close();
    }
}

创建客户端

客户端通过Socket连接到服务器，并发送和接收消息。

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

public class Client {
    public static void main(String[] args) throws IOException {
        String host = "localhost";
        int port = 12345;

        Socket socket = new Socket(host, port);
        System.out.println("已连接到服务器");

        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        String userInput;
        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput);
            System.out.println("服务器回复: " + in.readLine());
        }

        in.close();
        out.close();
        socket.close();
    }
}

处理多客户端连接

服务器端可以通过多线程处理多个客户端连接。

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

public class MultiThreadServer {
    public static void main(String[] args) throws IOException {
        int port = 12345;
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("服务器启动，等待客户端连接...");

        while (true) {
            Socket clientSocket = serverSocket.accept();
            System.out.println("客户端已连接");
            new Thread(new ClientHandler(clientSocket)).start();
        }
    }
}

class ClientHandler implements Runnable {
    private Socket clientSocket;

    public ClientHandler(Socket socket) {
        this.clientSocket = socket;
    }

    public void run() {
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);

            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                System.out.println("收到客户端消息: " + inputLine);
                out.println("服务器回复: " + inputLine);
            }

            in.close();
            out.close();
            clientSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用Socket发送和接收文件

通过Socket可以实现文件传输功能。

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

public class FileServer {
    public static void main(String[] args) throws IOException {
        int port = 12345;
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("服务器启动，等待客户端连接...");

        Socket clientSocket = serverSocket.accept();
        System.out.println("客户端已连接");

        InputStream in = clientSocket.getInputStream();
        FileOutputStream fileOut = new FileOutputStream("received_file.txt");

        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = in.read(buffer)) != -1) {
            fileOut.write(buffer, 0, bytesRead);
        }

        fileOut.close();
        in.close();
        clientSocket.close();
        serverSocket.close();
    }
}

public class FileClient {
    public static void main(String[] args) throws IOException {
        String host = "localhost";
        int port = 12345;

        Socket socket = new Socket(host, port);
        System.out.println("已连接到服务器");

        FileInputStream fileIn = new FileInputStream("file_to_send.txt");
        OutputStream out = socket.getOutputStream();

        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = fileIn.read(buffer)) != -1) {
            out.write(buffer, 0, bytesRead);
        }

        fileIn.close();
        out.close();
        socket.close();
    }
}

注意事项

• 确保端口未被占用，避免BindException。
• 处理异常情况，如连接中断或超时。
• 使用多线程或线程池处理多个客户端连接，避免阻塞主线程。
• 关闭所有资源（如Socket、流等），防止资源泄漏。