java-网络编程

TCP传递文字

客户端

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

public class TCPClientDemo1 {

    public static void main(String[] args) throws UnknownHostException {
        //要连接服务器需要知道服务器的ip和port
        InetAddress ip = InetAddress.getByName("127.0.0.1");
        int port = 9999;
        Socket socket = null;
        OutputStream os = null;

        //需要创建套接字用来连接
        try {
            socket = new Socket(ip, port);
            //发送信息的IO流
            os = socket.getOutputStream();
            os.write("hello world!".getBytes());


        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(os != null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(socket != null){
                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;

public class TCPServerDemo1 {
    public static void main(String[] args){
        //提升一下作用域
        ServerSocket serverSocket = null;
        Socket accept = null;
        InputStream is = null;
        ByteArrayOutputStream byteArrayOutputStream = null;

        //需要提供套接字（插座）给客户端
        try {
            serverSocket = new ServerSocket(9999);
            //等待客户端连接过来,下面的accept就是和客户端的socket配对的套接字

            //多次接收
            while(true) {
                accept = serverSocket.accept();
                //接收信息
                is = accept.getInputStream();
                //管道流
                byteArrayOutputStream = new ByteArrayOutputStream(); //该流可以将信息写入到内存
                byte[] buffer = new byte[1024];
                int len;
                while ((len = is.read(buffer)) != -1) {
                    byteArrayOutputStream.write(buffer, 0, len);
                }

                System.out.println(byteArrayOutputStream.toString());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //关闭流
            if(byteArrayOutputStream != null){
                try {
                    byteArrayOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(is != null){
                try {
                    is.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();
                }
            }
        }
    }
}

UDP消息发送

客户端

import java.io.IOException;
import java.net.*;

public class UDPClientDemo1 {
    public static void main(String[] args) throws IOException {
        DatagramSocket datagramSocket = new DatagramSocket();

        //包的信息如下
        String msg = "hello world!";
        InetAddress ip = InetAddress.getByName("127.0.0.1");
        int port = 9000;

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

        datagramSocket.send(packet);
    }
}

服务器

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

public class UDPServerDemo1 {
    public static void main(String[] args) throws IOException {
        DatagramSocket datagramSocket = new DatagramSocket(9000);

        //接收包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

        datagramSocket.receive(packet);

        System.out.println(new String(packet.getData()));
    }
}

UDP聊天通信

客户端

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


public class UDPClientDemo2 {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket();

        //使用控制台读取数据
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        while (true) {
            String dataString = reader.readLine();
            byte[] data = dataString.getBytes();
            DatagramPacket packet = new DatagramPacket(data, 0, data.length, new InetSocketAddress("127.0.0.1", 8888));

            socket.send(packet);
            if(dataString.equals("bye")){
                break;
            }

        }
        socket.close();
    }
}

服务端

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

public class UDPServerDemo2 {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket(8888);

        while (true) {
            byte[] buffer = new byte[1024];
            DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
            socket.receive(packet);

            //对读取到的数据进行判断方便结束
            String receiveData = new String(packet.getData(), 0, packet.getLength());
            //假如使用packet.getData().length，那么获得的长度会是1024

            System.out.println(receiveData);

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

通过URL下载文件

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

public class URLDemo {
    public static void main(String[] args) throws IOException {
        URL url = new URL("https://m701.music.126.net/20201013155815/4716d8336da1c8f4c84ef7db472c593b/jdyyaac/0f0c/5509/5309/8fd58bdf65bc94fd7e89dc7dbd4df522.m4a");

        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fileOutputStream = new FileOutputStream("op.m4a");
        byte[] buffer = new byte[1024];
        int len;
        while((len = inputStream.read(buffer)) != -1){
            fileOutputStream.write(buffer, 0, len);
        }

        //close stream
        fileOutputStream.close();
        inputStream.close();
        urlConnection.disconnect();
    }
}