Java学习day12

目录

• TCP
  • Tomcat
• UDP
  • UdpSendDemo01
  • UdpReceiveDemo01
  • 循环发送和接收
    • UdpSenderDemo01
    • UdpReceiveDemo01
  • 在线咨询
    • TalkSend
    • TalkReceive
    • TalkTeacher
    • TalkStudent
• URL
  • UrlDown

TCP

Tomcat

服务端

• 自定义 S
• Tomcat服务器 S：java后台开发
  客户端
• 自定义 C
• 浏览器 B
  
  
  

UDP

发短信：不用链接，但是需要知道对方的地址
Datagram Packet&&Datagram Socket

UdpSendDemo01

//不需要连接服务器
public class UdpSendDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立一个Socket
        DatagramSocket socket = new DatagramSocket();


        //2.建个包
        String msg = "你好服务器";

        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port=9090;
        // 数据，数据包长度起始，要发送给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length,localhost,9090);

        //3.发送包
        socket.send(packet);

        //4.关闭流
        socket.close();
    }

}

UdpReceiveDemo01

//等待客户端的链接
public class UdpReceiveDemo01 {
    public static void main(String[] args) throws Exception {
        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);//接收

        socket.receive(packet);//阻塞接受

        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0,packet.getLength()));

        //关闭连接
        socket.close();


    }
}

运行结果：
127.0.0.1
你好服务器

UDP不需要建立连接，也没有客户端和服务端的概念，只有发送端和接收端

循环发送和接收

UdpSenderDemo01

public class UdpSenderDemo01 {
    public static void main(String[] args) throws Exception {

        DatagramSocket socket = new DatagramSocket(8888);

        //准备数据：控制台读取System.in

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        while (true) {
            String data = reader.readLine();
            byte[] datas = data.getBytes();
            DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress("localhost",6666));

            socket.send(packet);

            if (data.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

UdpReceiveDemo01

public class UdpReceiveDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);



        while (true) {
            //准备接受包裹
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container,0,container.length);
            socket.receive(packet);//阻塞式接受包裹

            //断开连接 bye
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);
            System.out.println(receiveData.trim());

            if(receiveData.trim().equals("bye")){
                break;
            }

        }
        socket.close();


    }
}

接收端在判断时用.trim去除多余空格

运行结果：
Sender输入：
test1
test2
bye
程序结束

Receive接收：
test1
test2
bye
程序结束

在线咨询

TalkSend

public class TalkSend implements Runnable {
    DatagramSocket socket = null;
    BufferedReader reader = null;

    private int fromPort;
    private String toIP;
    private int toPort;

    public TalkSend(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() {
        while (true) {
            try {
                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;
                }

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


        }
        socket.close();
    }
}

TalkReceive

public class TalkReceive implements Runnable{

    DatagramSocket socket = null;
    private int port;
    private String msgFrom;


    public TalkReceive(int port,String msgFrom){
        this.port=port;
        this.msgFrom=msgFrom;
        try {
            socket = new DatagramSocket(this.port);
        } catch (SocketException e) {
            e.printStackTrace();
        }

    }
    @Override
    public void run() {

        while (true) {
            try {
                //准备接受包裹
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container,0,container.length);
                socket.receive(packet);//阻塞式接受包裹

                //断开连接 bye
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);
                System.out.println(msgFrom+":"+receiveData.trim());

                if(receiveData.trim().equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
        socket.close();


    }
}

TalkTeacher

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

TalkStudent

public class TalkStudent {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend(7777,"localhost",9999)).start();
        new Thread(new TalkReceive(8888,"老师")).start();
    }
}

这样就可以实现双方实时交流
注：

1. 同一个实例，发送的端口和接受的端口不是一个端口。
2. 本例中TalkReceive中的msgFrom对象，是接收方写的，是本地定义接收到的消息的发送方的名称。
3. 线程确实好用，有更加深刻的认识。
4. 如本地和对方电脑各自打开端口，应该可以用此程序和IP及端口号完成信息的传输。

URL

统一资源定位符：定位资源的，定位互联网上的某一个资源
DNS：域名解析 www.baidu.com -> xxx.x..x..x

https://www.baidu.com
协议://ip地址：端口/项目名/资源

UrlDown

public class UrlDown {
    public static void main(String[] args) throws Exception {
        //1.下载地址

        //URL url = new URL("http://localhost:8080/hufo/Security.txt");
        URL url = new URL("https://m801.music.126.net/20211219174439/ab07c905816680e1bbe177a25affa306/jdyyaac/050b/0e5e/040f/2ac9f88e439461bdc4f23e6ed61ccbe9.m4a");

        //2.连接到这个资源HTTP
        HttpURLConnection urlConnection =(HttpURLConnection) url.openConnection();

        InputStream inputStream = urlConnection.getInputStream();
        
        //FileOutputStream fos = new FileOutputStream("SecurityText.txt");
        FileOutputStream fos = new FileOutputStream("a spring without you.m4a");
        
        byte[] buffer = new byte[1024];
        int len;
        while((len=inputStream.read(buffer))!=-1){
            fos.write(buffer,0,len);//写出这个数据
        }

        fos.close();
        inputStream.close();
        urlConnection.disconnect();//断开连接
    }
}

这样就能直接从网页下载资源了，如果下载别的音乐、视频，浏览器中点击F12打开开发者模式，在网络里找到对应格式的文件，复制名字，在最前面加上“/”，并加在当前网址的最后，然后就可以通过URL下载。