Java从入门到精通 第19章 网络通信

网络程序设计基础

• TCP/IP协议中有两种协议：TCP、UDP
• 端口和套接字
  • 端口：0-65535，通过不同的端口连接不同的服务，HTTP80，FTP21，
  • 套接字： 用来连接应用程序与端口，类似于插座连接电线与电器

TCP程序设计基础

java.net.InetAdress类，与IP地址相关的类，InetAdress类的方法会抛出UnknownHostException，所以必须进行异常处理

java.net.ServerSocket类用于表示服务器套接字

UDP程序设计基础

java.net.DatagramPacket类表示数据包，java.net.DatagramSocket类表示发送和接受数据包的套接字

package ex19_Net;

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

public class InetAdress_test {
    public static void main(String args[]) {
        InetAddress ip;
        try {
            ip = InetAddress.getLocalHost();
            String localname = ip.getHostName();
            String localip = ip.getHostAddress();
            System.out.println("name: " + localname);
            System.out.println("ip: " + localip);


        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }


}

package ex19_Net;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class TCP_test {
    private BufferedReader reader;
    private ServerSocket server;
    private Socket socket;
    void getserver() {
        try {
            server = new ServerSocket(8998);
            System.out.println("服务器套接字创建成功");
            while (true) {
                System.out.println("等待客户机的连接");
                socket = server.accept();
                reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                getClientMessage();
            }

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

    private void getClientMessage() {
        try {
            while (true) {
                System.out.println("客户机：" + reader.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            if (reader != null) {
                reader.close();
            }
            if (socket != null) {
                socket.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]) {
        TCP_test tcp = new TCP_test();
        tcp.getserver();
    }

}

package ex19_Net;

import javax.swing.*;
import javax.swing.border.BevelBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.PrintWriter;
import java.net.Socket;

public class TCP_test_client extends JFrame {
    private PrintWriter writer;
    Socket socket;
    private JTextArea ta = new JTextArea();
    private JTextField tf = new JTextField();
    Container cc;
    public TCP_test_client(String title) {
        super(title);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        cc = this.getContentPane();
        final JScrollPane scrollPane = new JScrollPane();
        scrollPane.setBorder(new BevelBorder(BevelBorder.RAISED));
        getContentPane().add(scrollPane, BorderLayout.CENTER);
        scrollPane.setViewportView(ta);
        cc.add(tf,"South");
        tf.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                writer.println(tf.getText());
                ta.append(tf.getText() + '\n');
                ta.setSelectionEnd(ta.getText().length());
                tf.setText("");
            }
        });
    }

    private void connect() {
        ta.append("尝试连接\n");
        try {
            socket = new Socket("127.0.0.1",8998);
            writer = new PrintWriter(socket.getOutputStream(),true);
            ta.append("完成连接\n");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]) {
        TCP_test_client client = new TCP_test_client("向服务器发生数据");
        client.setSize(200,200);
        client.setVisible(true);
        client.connect();
    }
}