JAVA网络编程

JAVA网络编程

网络编程

1.1 概述

1.2 网络通信要素

问题:

  • 如何准确定位到一台或者多台主机
  • 找到主机之后如何进行通信

网络编程的要素:

  • IP和端口号(ip)
  • 网络通信协议(tcp/udp)

1.3 IP地址(InetAddress)

特殊IP地址:

  • 127.0.0.1:本机localhost
  • ip地址分类:
    • IPV4/IPV6
      • IPV4:4个字节组成
      • IPV6:8个无符号整数,128位
    • 公网(互联网)/私网(局域网)
      • 192.168.xx.xx:专门给组织内部使用(局域网)

InetAddress中没有构造器,需要用他的静态方法返回本身

package ip_study;

import java.net.InetSocketAddress;

public class TestInetSocketAddress {
    public static void main(String[] args) {
        InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1",8080);
        System.out.println(inetSocketAddress);

        System.out.println(inetSocketAddress.getAddress());
        System.out.println(inetSocketAddress.getHostName());

    }
}

1.4 端口

端口表示计算机上的一个程序的进程

  • 不同的进程有不同的端口号:用来区分软件

  • 被规定0~65535

  • 分为TCP端口和UDP端口:每个都有65535,单个协议下面端口号不能冲突

  • 端口分类:

    • 公有端口:0~1023
      • http:80
      • https:443
      • ftp:21
      • telent:23
    • 程序注册端口:1024~49151:分配给用户或者程序的
      • Tomcat:8080
      • MySQL:3306
      • Orcale:1521
    • 动态、私有:49152~65535
    netstat -ano #查看所有的端口
    netstat -ano|findstr "5900" #查看指定的端口
    tasklist|findstr"8696" #查看指定端口的进程
    
    package ip_study;
    
    import java.net.InetSocketAddress;
    
    public class TestInetSocketAddress {
        public static void main(String[] args) {
            InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1",8080);
            System.out.println(inetSocketAddress);
    
            System.out.println(inetSocketAddress.getAddress());
            System.out.println(inetSocketAddress.getHostName());
    
        }
    }
    

1.5 通信协议

TCP/IP协议簇:实际上是一组协议

  • 重要:
    • TCP:用户传输协议
    • UDP:用户数据报协议
  • 出名的协议:
    • TCP:
    • IP:网络互连协议

TCP UDP对比:

  • tcp:打电话

    • 连接稳定
    • 三次握手,四次挥手
    最少需要三次,保证稳定连接
    A:你瞅啥
    B:瞅你咋地
    A:干一场
    
    
    A:我要走了
    B:你真的要走了吗
    B:你真的真的要走了吗
    A:我真的要走了
    
    • 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:没有明确的界限
    • 不管有没有准备好,都可以发给你

1.6 TCP实现聊天

客户端

  1. 连接服务器:Socket
  2. 发送消息
package tcp_study;

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

public class TcpClientDemo01 {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            //要知道服务器的地址
            InetAddress serverIP = InetAddress.getByName("localhost");
           int port = 9999;
            //创建一个socket连接
            socket = new Socket(serverIP,port);
            //发送消息 IO流
            os = socket.getOutputStream();
            os.write("发送方发送啦".getBytes());

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

    }
}

服务器

1. 建立服务端口ServerSocket
2. 等待用户的链接:accept
3. 接受用的消息:输入流(管道流)
package tcp_study;

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

public class TcpServerDemo01 {
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        ByteArrayOutputStream baos = null;
        InputStream is = null;
        Socket socket = null;

        try {
            //得有个地址
            serverSocket = new ServerSocket(9999);
            while(true) {
                //等待客户端连接过来
                socket = serverSocket.accept();
                //读取客户端的消息
                is = socket.getInputStream();

                //管道流
                baos = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024];
                int len;
                while ((len = is.read(buffer)) != -1) {
                    baos.write(buffer, 0, len);
                }
                System.out.println(baos.toString());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //关闭资源
            if(baos!=null){
                try {
                    baos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(is!=null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

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

        }
    }
}

1.7 TCP实现文件上传

//服务器端
package ip_tofile_study;

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

public class TcpServerDemo2 {
    public static void main(String[] args) throws IOException {
        //创建服务
        ServerSocket serverSocket = new ServerSocket(9000);
        //监听客户端连接
        Socket socket = serverSocket.accept();//阻塞式监听,会一直等待客户端连接
        //获取输入流
        InputStream is = socket.getInputStream();

        //文件输出
        FileOutputStream fos = new FileOutputStream(new File("receive.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while((len = is.read(buffer))!=-1){
            fos.write(buffer,0,len);
        }

        //通知客户端接受完毕了
        OutputStream os = socket.getOutputStream();
        os.write("我接收完毕了".getBytes());
        //关闭资源
        fos.close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}
//客户端
package ip_tofile_study;

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

public class TcpClientDemo2 {
    public static void main(String[] args) throws IOException {
        //创建一个socket链接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9000);
        //创建一个输出流
        OutputStream os = socket.getOutputStream();
        //读取文件
        FileInputStream fis = new FileInputStream(new File("椎名真白.jpg"));
        //写出文件
        byte[] buffer = new byte[1024];
        int len;
        while((len = fis.read(buffer))!=-1){
            os.write(buffer,0,len);
        }
        //通知服务器,我已经传输完了
        socket.shutdownOutput();//我已经传输完了

        //确定服务器接受完毕,才能断开连接
        InputStream inputStream = socket.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer2 = new byte[1024];
        int len2;
        while((len2=inputStream.read(buffer2))!=-1){
            baos.write(buffer,0,len2);
        }

        //关闭资源
        baos.close();
        inputStream.close();
        fis.close();
        os.close();
        socket.close();

    }
}

1.8 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

1.9 UDP

发短信:不用链接,需要对方的地址

一端发给另外一端

发送端


package udp_study;

import java.io.IOException;
import java.net.*;
import java.nio.charset.StandardCharsets;

public class UdpClientDemo01 {
    public static void main(String[] args) throws IOException {
        //建立一个Socket
        DatagramSocket socket = new DatagramSocket();
        //建一个包
        String msg = "你好啊,服务器!";
        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;
        //参数:数据,数据的长度起始,要发送的IP地址和端口
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);

        //发送包
        socket.send(packet);

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

接收端


package udp_study;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
//还是要等待客户端的连接
public class UdpServerDemo01 {
    public static void main(String[] args) throws IOException {
        //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);
        socket.receive(packet);//阻塞接受
        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0,packet.getLength()));
        //关闭资源
        socket.close();
    }
}

一端循环发送消息

发送端


package chat;

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

public class UdpSenderDemo01 {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket(8888);
        //准备数据:控制台读取
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        while(true) {
            String data = reader.readLine();
            byte[] datas = data.getBytes();//数据只有转化成字节才可以读
            DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress("localhost", 6666));
            socket.send(packet);
            if(data.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

接收端


package chat;

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

public class UdpReceiverDemo01 {
    public static void main(String[] args) throws IOException {
        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);
            //断开连接
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);
            System.out.println(receiveData);
            if(receiveData.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

在线咨询

两个人都可以是发送方也都可以是接受方

场景:老师给学生发消息

说明:

  • 因为是相互发消息,所以不存在发送方和接收方
  • 每个用户都可以发送或者接受消息,利用双线程完成

简要设计:

包含四个类:发送类,接受类,老师类,学生类

  • 发送类:完成包的发送
    • 成员变量:发送方端口,接收方端口,接收方IP
    • 循环发送
  • 接受类:完成包的接收
    • 成员变量:接收方端口,发送方昵称
    • 循环接收
  • 老师类和学生类均使用双线程,注意开放的端口号不同

//talksend类
package chat;

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) {
            String data = null;
            try {
                data = reader.readLine();
                byte[] datas = data.getBytes();//数据只有转化成字节才可以读
                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类
package chat;

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.msgFrom = msgFrom;
        this.port = port;
        try {
            socket = new DatagramSocket(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);
                //断开连接
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);
                System.out.println(msgFrom+":"+receiveData);
                if(receiveData.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}
//学生
package chat;

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();
    }
}
//老师
package chat;

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();
    }
}

2.0 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:将域名解析成IP

协议://IP地址:端口/项目名/资源

url下载歌曲江南


package url_study;

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

public class UrlDownLoad {
    public static void main(String[] args) throws Exception {
        //得到url
        URL url = new URL("https://m10.music.126.net/20210527215758/9bc4d608a8a0cd7bb60cbebb9e45049a/yyaac/obj/wonDkMOGw6XDiTHCmMOi/3047335779/c10c/e3a7/4c42/719b0c3fcba91b78ad27ace8be81c3e4.m4a");
        //建立http连接
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        //输入流得到资源
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("江南.m4a");
        byte[] buffer =new byte[1024];
        int len;
        while((len = inputStream.read(buffer))!=-1){
            fos.write(buffer,0,len);
        }
        fos.close();
        inputStream.close();
        urlConnection.disconnect();
    }
}