Java基础语法-网络编程

网络编程中的要素:

1.IP和端口号。

2.网络通信协议：TCP/UDP。

一、InetAddress：此类表示Internet协议（IP）地址

代码示例：

public static void main(String[] args) throws UnknownHostException {
    InetAddress byName = InetAddress.getByName("127.0.0.1");
    System.out.println(byName);//返回结果：/127.0.0.1

    InetAddress byName1 = InetAddress.getByName("www.baidu.com");
    System.out.println(byName1);//返回结果：www.baidu.com/61.135.169.125

    //获取ip
    System.out.println(byName1.getHostAddress());
    //获取域名
    System.out.println(byName1.getHostName());
}

二、端口

端口表示计算机上的一个程序的进程：

1.不同的进程有不同的端口号。

2.被规定 0~65535。

3.TCP/UDP 65535*2, TCP:80，UDP:80，单个协议下，端口号不能冲突。

4.端口分类：

公共端口：0~1023

    HTTP：80

    HTTPS：443

    FTP：21

    Telent：23

程序注册端口：1024~49151，分配用户或者程序。

    Tomcat：8080

    MySql：3306

    Oracle：1521

动态、私有：49152~65535

三、通信协议

TCP：

连接，稳定。

三次握手、四次挥手：最少需要三次，保证稳定连接。至少需要四次，保证断开。

客户端、服务端。

传输完成、释放连接、效率低。

UDP：

不连接，不稳定。

客户端、服务器：没有明确的界限。

四、TCP

客户端

1.连接服务器Socket

2.发送消息

服务器

1.建立服务的端口 ServerSocket

2.等待用的的连接 accept

3.接收消息

客户端代码示例：

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

/**
 * @ClassName TcpClient
 * @Description 客户端
 * @Author
 * @Date 2020-06-15 10:43
 * @Version 1.0
 **/
public class TcpClient {
    public static void main(String[] args) throws Exception {
        InetAddress inetAddress = null;
        Socket socket = null;
        OutputStream outputStream = null;
        try {
            //调用服务端的地址
            inetAddress = InetAddress.getByName("127.0.0.1");
            //创建Socket连接
            socket = new Socket(inetAddress, 9999);
            outputStream = socket.getOutputStream();
            outputStream.write("hello world".getBytes());
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //关闭资源
            if(outputStream != null){
                try {
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }
}

服务端代码示例：

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @ClassName TcpServer
 * @Description 服务端
 * @Author ywl
 * @Date 2020-06-15 10:43
 * @Version 1.0
 **/
public class TcpServer {
    public static void main(String[] args){
        ServerSocket serverSocket = null;
        Socket accept = null;
        InputStream inputStream = null;
        ByteArrayOutputStream byteArrayOutputStream = null;
        try{
            //设置地址
            serverSocket = new ServerSocket(9999);
            //连接客户端
            accept = serverSocket.accept();
            //读取客户端消息
            inputStream = accept.getInputStream();

            byteArrayOutputStream = new ByteArrayOutputStream();

            byte[] bytes = new byte[1024];

            int len;

            while ((len = inputStream.read(bytes)) != -1) {
                byteArrayOutputStream.write(bytes, 0, len);
                System.out.println(byteArrayOutputStream.toString());
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            //关闭资源
            if(byteArrayOutputStream != null){
                try {
                    byteArrayOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(inputStream != null){
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(accept != null){
                try {
                    accept.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(serverSocket != null){
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }


    }
}

四、UDP

代码示例：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/**
 * @ClassName UdpClient
 * @Description Udp
 * @Author
 * @Date 2020-06-15 13:12
 * @Version 1.0
 **/
public class UdpClient {
    public static void main(String[] args) {
        DatagramSocket datagramSocket = null;
        try {
            //创建一个Socket
            datagramSocket = new DatagramSocket();
            //发送
            InetAddress inetAddress = InetAddress.getByName("localhost");
            //创建Packet
            DatagramPacket datagramPacket = new DatagramPacket("hello word!您好".getBytes(), 0, "hello word!您好".getBytes().length, inetAddress, 9090);
            //发送Packet
            datagramSocket.send(datagramPacket);

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if(datagramSocket != null){
                datagramSocket.close();
            }
        }
    }
}

import java.net.DatagramPacket;
import java.net.DatagramSocket;

/**
 * @ClassName UdpServer
 * @Description TODO
 * @Author
 * @Date 2020-06-15 13:20
 * @Version 1.0
 **/
public class UdpServer {
    public static void main(String[] args) {
        try {
            //开放端口
            DatagramSocket datagramSocket = new DatagramSocket(9090);
            byte[] bytes = new byte[1024];
            DatagramPacket datagramPacket = new DatagramPacket(bytes, 0, bytes.length);
            datagramSocket.receive(datagramPacket);

            System.out.println(new String(datagramPacket.getData(),0,datagramPacket.getLength()));

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

五、UDP多线程聊天

发送工具类：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

/**
 * @ClassName TalkSendUtils
 * @Description UDP发送
 * @Author
 * @Date 2020-06-15 13:50
 * @Version 1.0
 **/
public class TalkSendUtils implements Runnable{

    private DatagramSocket socket = null;
    private BufferedReader reader = null;

    private int fromPort;
    private String toIp;
    private int toPort;

    public TalkSendUtils(int fromPort, String toIp, int toPort) {
        this.fromPort = fromPort;
        this.toIp = toIp;
        this.toPort = toPort;

        try {

            socket = new DatagramSocket(fromPort);
            reader = new BufferedReader(new InputStreamReader(System.in));

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


    }

    @Override
    public void run() {
        try {
            while(true){
                String data = reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress(this.toIp, this.toPort));
                socket.send(packet);
                if(data.equals("bye")){
                    break;
                }
            }
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

接受工具类：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * @ClassName TalkReceiveUtils
 * @Description 接受工具类
 * @Author
 * @Date 2020-06-15 14:02
 * @Version 1.0
 **/
public class TalkReceiveUtils implements Runnable{
    private DatagramSocket socket = null;
    private int port;
    private String fromName;

    public TalkReceiveUtils(int port,String fromName) {
        this.port = port;
        this.fromName = fromName;

        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        try {
            while (true){
                byte[] bytes = new byte[1024];
                DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length);
                socket.receive(packet);
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);
                System.out.println(fromName+"："+receiveData);
                if (receiveData.equals("bye")){
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

测试类：

public static void main(String[] args) {
    new Thread(new TalkSendUtils(7777,"localhost",9999)).start();
    new Thread(new TalkReceiveUtils(8888,"老师")).start();
}

public static void main(String[] args) {
    new Thread(new TalkSendUtils(5555,"localhost",8888)).start();
    new Thread(new TalkReceiveUtils(9999,"学生")).start();
}

六、URL

统一资源定位符。

代码示例如下：

public static void main(String[] args) {
    try {
        URL url = new URL("https://eu-sycdn.kuwo.cn/0a79505fd846f2b6f1019dd2086d38dd/5ee723f9/resource/n2/22/35/1153965333.mp3");
        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fileOutputStream = new FileOutputStream("E:\\1153965333.mp3");
        byte[] bytes = new byte[1024];
        int len;
        while ((len = inputStream.read(bytes)) != -1){
            fileOutputStream.write(bytes,0,len);
        }
        fileOutputStream.close();
        inputStream.close();
        urlConnection.disconnect();
    } catch (Exception e) {
        e.printStackTrace();
    }
}