public class TestInetAddress {
    public static void main(String[] args) {
        try {
            //查詢網(wǎng)站IP地址
            InetAddress ip1 = InetAddress.getByName("www.baidu.com");
            System.out.println(ip1);//www.baidu.com/163.177.151.109
            //查詢本機
            InetAddress ip2 = InetAddress.getLocalHost();
            System.out.println(ip2);//飛雷神/192.168.153.1
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }

    }
}

形象記憶
三次握手（連接）
A:你愁啥？	 發(fā)送請求
B:瞅你咋地？	回應(yīng)請求
A:來干一場！	確認鏈接


四次揮手：（斷開）

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

//客戶端
public class TcpClientDemo01 {

    private static OutputStream os;
    private static Socket socket;

    public static void main(String[] args) {

        try {
            //1.獲得服務(wù)器的地址、端口號
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port=9999;//服務(wù)器的端口號
            //2.創(chuàng)建一個Sock連接
            socket = new Socket(serverIP,port);
            //使用該鏈接發(fā)送IO流消息
            os = socket.getOutputStream();
            os.write("你好,吃飯了嗎？".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }finally {//關(guān)閉資源
            if(os!=null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import com.sun.xml.internal.messaging.saaj.util.ByteOutputStream;

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

public class TcpServerDemo01 {

    private static ServerSocket serverSocket;
    private static Socket socket;
    private static InputStream stream;
    private static ByteOutputStream baos;

    public static void main(String[] args) throws IOException {
        try {
            //給自己一個地址，端口號
            serverSocket = new ServerSocket(9999);
            while(true) {
                //等待客戶端連接
                socket = serverSocket.accept();
                //讀取客戶端的消息
                stream = socket.getInputStream();

                //管道流
                baos = new ByteOutputStream();
                byte[] bytes = new byte[1024];
                int len;
                while ((len = stream.read(bytes)) != -1) {
                    baos.write(bytes, 0, len);
                }
                System.out.println(baos.toString());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            baos.close();
            try {
                stream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            serverSocket.close();
        }

    }
}

import com.sun.xml.internal.messaging.saaj.util.ByteOutputStream;
import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

public class TcpClientDemo02 {
    public static void main(String[] args) throws Exception {
        //創(chuàng)建一個Socket連接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9000);
        //socket的輸出流
        OutputStream os = socket.getOutputStream();
        //讀取文件的流
        FileInputStream fis = new FileInputStream("bg.jpeg");
        //寫出文件

        byte[] bytes = new byte[1024];//緩沖區(qū)
        int len;
        while ((len = fis.read(bytes)) != -1) {//讀到緩沖區(qū)
            os.write(bytes, 0, len);//從緩沖區(qū)寫到輸出流
        }

        //通知服務(wù)器，我已經(jīng)上傳完成
        socket.shutdownOutput();

        //接收確定服務(wù)器接收完畢的信息，斷開連接
        InputStream inputStream = socket.getInputStream();
        ByteOutputStream bost = new ByteOutputStream();
        byte[] bytes2 = new byte[1024];
        int len2;
        while ((len2 = inputStream.read(bytes2)) != -1) {
            bost.write(bytes2,0,len2);
        }
        System.out.println(bost.toString());

        //關(guān)閉資源
        bost.close();
        inputStream.close();
        fis.close();
        os.close();
        socket.close();
    }
}

package com.yong.tcp;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TcpServerDemo02 {
    public static void main(String[] args) throws IOException {
        //創(chuàng)建鏈接
        ServerSocket serverSocket = new ServerSocket(9000);
        //監(jiān)聽客戶端的連接
        Socket socket = serverSocket.accept();
        //獲取輸入流
        InputStream inputStream = socket.getInputStream();//阻塞式監(jiān)聽，會一直等待

        //文件輸出
        FileOutputStream fos = new FileOutputStream("receiver.jpeg");
        byte[] bytes = new byte[1024];
        int len;
        while ((len = inputStream.read(bytes)) != -1) {
            fos.write(bytes, 0, len);
        }

        //通知客戶端，我已接收完畢
        OutputStream os = socket.getOutputStream();
        os.write("我接收完畢了，可以斷開鏈接了".getBytes());

        //關(guān)閉資源
        os.close();
        fos.close();
        inputStream.close();
        socket.close();
        serverSocket.close();

    }
}

package com.yong.chat;

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

public class ChatSendDemo01 {
    public static void main(String[] args) throws Exception {
        //建立一個端口
        DatagramSocket socket = new DatagramSocket(8888);

        //建立一個包裹
        //準(zhǔn)備數(shù)據(jù)，從控制臺
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        while (true) {

            String data = reader.readLine();//控制臺控制輸入
            byte[] datas = data.getBytes();
            DatagramPacket packet = new DatagramPacket(datas, 0, data.length(), new InetSocketAddress("localhost", 9999));

            //發(fā)送包裹
            socket.send(packet);

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

        }
        socket.close();
    }
}

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

public class ChatReceiverDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9999);

        while (true) {

            //準(zhǔn)備接收包裹
            byte[] bytes = new byte[1024];
            DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length);

            socket.receive(packet);//阻塞式接受包裹
            byte[] data = packet.getData();//拿出消息
            String receiveData = new String(data, 0, data.length);//轉(zhuǎn)為字符串，注意不要導(dǎo)錯包

            System.out.println(receiveData);

            //退出接收
            if ("bye".equals(receiveData.trim())) {
                break;
            }

        }
        socket.close();
    }
}

import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class UrlDown {
    public static void main(String[] args) throws Exception {
        //下載地址，
        URL url = new URL("https://m701.music.126.net/20210813190206/833ba2325a035b223f2f315a7a5b1d4f/jdyyaac/0353/055e/565e/4910a621a524e5158013a4ccdad535d9.m4a");

        //連接到這個資源
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        InputStream is = connection.getInputStream();
        FileOutputStream fos = new FileOutputStream("富士山下（陳奕迅）.m4a");


        byte[] bytes = new byte[1024];
        int len;
        while ((len = is.read(bytes)) != -1) {
            fos.write(bytes, 0, len);
        }

        fos.close();
        is.close();
        connection.disconnect();//斷開連接
    }
}