网络编程丶

计算机网络

TCP:打电话

• 连接，稳定
• 三次握手，四次挥手
• 客户端，服务端
• 传输完成，释放连接，效率低

UDP:发短信

• 不连接，不稳定
• 客户端，服务端，无明确界限
• DDOS：饱和攻击

TCP实现聊天

客户端

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

//客户端
public class TcpClientDemo01 {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            socket = new Socket(serverIP, port);
            os = socket.getOutputStream();
            os.write("hi world".getBytes());
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != os) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != socket) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

服务端

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

//服务端
public class TcpServerDemo01 {
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket accept = null;
        InputStream is = null;
        try {
            serverSocket = new ServerSocket(9999);
            while (true) {
                //死循环 等待客户端连接过来
                accept = serverSocket.accept();
                is = accept.getInputStream();
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024];
                int len;
                while (-1 != (len = is.read(buffer))) {
                    baos.write(buffer, 0, len);
                }
                System.out.println(baos.toString());
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != is) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != accept) {
                try {
                    accept.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != serverSocket) {
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

TCP实现文件上传

客户端

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

//客户端
public class TcpClientDemo02 {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        InputStream inputStream = null;
        ByteArrayOutputStream baos = null;
        try {
            socket = new Socket(InetAddress.getByName("127.0.0.1"), 9999);
            os = socket.getOutputStream();
            //读取文件 父工程的根目录下
            FileInputStream fis = new FileInputStream(new File("tb.jpg"));//管道流
            //写出文件
            byte[] buffer = new byte[1024];
            int len;
            while (-1 != (len = fis.read(buffer))) {
                os.write(buffer, 0, len);
            }
            //通知服务器，我已经结束了
            socket.shutdownOutput();
            //确定服务器接收完毕，断开连接
            inputStream = socket.getInputStream();//阻塞式监听
            baos = new ByteArrayOutputStream();//各种类型的管道流供选择
            byte[] buffer2 = new byte[1024];
            int len2;
            while (-1 != (len2 = inputStream.read(buffer2))) {
                baos.write(buffer2, 0, len2);
            }
            System.out.println(baos.toString());
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != baos) {
                try {
                    baos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != inputStream) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != os) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != socket) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

服务端

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

//服务端
public class TcpServerDemo02 {
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket accept = null;
        InputStream is = null;
        FileOutputStream fos = null;
        OutputStream os = null;
        try {
            serverSocket = new ServerSocket(9999);
            accept = serverSocket.accept();//阻塞式监听
            //等待客户端连接过来
            is = accept.getInputStream();
            //把流写到服务器
            fos = new FileOutputStream(new File("receive.jpg"));
            byte[] buffer = new byte[1024];
            int len;
            while (-1 != (len = is.read(buffer))) {
                fos.write(buffer, 0, len);
            }
            //通知客户端 我接收完毕了
            os = accept.getOutputStream();
            os.write("我接收完毕了，你可以断开了".getBytes());

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != os) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != fos) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != is) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != accept) {
                try {
                    accept.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != serverSocket) {
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

UDP实现消息发送

发送端

import java.net.*;

public class UdpSendDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立一个socket
        DatagramSocket socket = new DatagramSocket();

        String msg = "你好啊，接收端";
        InetAddress address = InetAddress.getByName("localhost");
        int port = 9090;

        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, address, port);

        socket.send(packet);

        socket.close();
    }
}

接收端

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

public class UdpReciveDemo01 {
    public static void main(String[] args) throws Exception {
        
        DatagramSocket socket = new DatagramSocket(9090);
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

        socket.receive(packet);//阻塞接收

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

        socket.close();
    }
}

UDP实现消息循环发送

发送方

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

public class UdpSendDemo02 {
    public static void main(String[] args) throws Exception {
        //1.建立一个socket
        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();
    }
}

接收方

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

public class UdpReciveDemo02 {
    public static void main(String[] args) throws Exception {

        DatagramSocket socket = new DatagramSocket(6666);

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

            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);

            System.out.println(receiveData);

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

UDP实现消息互发

发送器

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

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();
    }
}

接收器

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

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(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        while (true) {
            try {
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
                socket.receive(packet);//阻塞式接收包裹
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);

                System.out.println(this.msgFrom+"："+receiveData);

                if (receiveData.equals("bye")) {
                    break;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

角色一

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

角色二

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();
    }
}

URL下载网络资源

下载网上的文件资源

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 {
        URL url = new URL("https://m10.music.126.net/20201104154250/187b2743b01dbfa7e8d1bc1460c8d81e/yyaac/005c/540c/0659/76d554a876cf0882482013c77516ef93.m4a");
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("3.m4a");

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

        fos.close();
        inputStream.close();
        urlConnection.disconnect();
    }
}