网络编程入门

网络编程

1.1概述

网络编程的目的：

实现信息交互

达到目的需要什么条件？

如何准确定位一台主机：IP
如何定位计算机上资源：端口
如何传输数据：

java web： B/S架构

应用：C/S架构

1.2网络通讯的要素

1.通信双方的地址：

IP
端口号

2.网络通信协议

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1.3 IP

ip地址：

唯一定位一台网络上的计算机
分类
1. IPV4 ：4个字节组成， 0~255，约42亿个（亚洲只有4亿，不公平）
2. IPV6 ：128位 , 8个无符号整数fe80::c0c0:ba57:fe79:a2a913
3. 公网：用于互联网
4. 私网：用于局域网
  1. 192.168.xxx.xxx属于局域网
5. 域名：用于记忆IP（越短越贵，超贵）

package com.mrh.net;

import java.net.InetAddress;
import java.net.UnknownHostException;

/**
 * TestInetAddress
 * 测试IP
 * 2020/4/13 21:18
 **/
public class TestInetAddress {
    public static void main(String[] args) {
        try{
            //根据域名或IP查询地址
            InetAddress inetAddress1 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress1);
            //www.baidu.com/183.232.231.174

            System.out.println(inetAddress1.getHostAddress());
            //183.232.231.174

            System.out.println(inetAddress1.getHostName());
            //www.baidu.com

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

1.4 端口

端口标识计算机上得一个程序的进程

不同的进程有不同的端口号，同来区分软件
0~65535
端口分类
- 公用端口0~1023
  - HTTP : 80
  - HTTPS : 443
  - FTP : 21
  - Telent : 23
- 程序注册端口：1024~49151,分配用户或程序
  - tomcat : 8080
  - Mysql : 3306
  - Oracle : 1521
- 动态/私有： 49152~65535
```
netstat -ano #查看所有端口

netstat -ano|findstr “5900”  #查看指定端口

tasklist|findstr “8696” #查看指定端口进程
```
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1.5 通信协议

协议：约定的规则

TCP/IP协议簇

TCP : 用户传输协议
UDP：数据报传输协议
IP:网络互连协议
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TCP UDP对比

TCP：打电话

连接，稳定
传输完成，释放连接，效率低
三次握手，四次挥手
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客户端，服务端

UDP：发短信

不链接，不稳定
客户端，服务端没有明确界限
不管有没有准备都可以发给你
不安全（饱和攻击）

1.6 TCP

TCP实现聊天

package com.mrh.net;

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

/**
 * TestSocketAddress
 * 测试客户端
 * 2020/4/13 21:38
 **/
public class TestClientDemo1 {
    public static void main(String[] args) throws IOException {

        //1.要知道服务器地址
        InetAddress inetAddress = InetAddress.getByName("localhost");
        int port = 9999;
        //2.创建一个socket连接
        Socket socket = new Socket(inetAddress, port);
        //3.发送消息 IO流
        OutputStream os = socket.getOutputStream();
        os.write("你好，我是帅比".getBytes());

        //关闭流
        if(os != null) {
            os.close();
        }
        if(socket != null) {
            socket.close();
        }

    }
}

package com.mrh.net;

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

/**
 * TestServerDemo1
 * 2020/4/13 22:05
 * 测试服务端
 **/
public class TestServerDemo1 {
    public static void main(String[] args) throws IOException {

        //1.要有一个地址
        ServerSocket serverSocket = new ServerSocket(9999);
        //等待客户端
        Socket socket = serverSocket.accept();
        //读取客户端信息
        InputStream is = socket.getInputStream();
        //管道流
        ByteArrayOutputStream 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());

        //关闭流
        if(baos != null) {
            baos.close();
        }
        if(is != null) {
            is.close();
        }
        if(socket != null) {
            socket.close();
        }
        if(serverSocket != null) {
            serverSocket.close();
        }

    }
}

文件上传

Tomcat

服务端

自定义
Tomcat

客户端

自定义
浏览器

1.7 UDP

UDP实现聊天

package com.mrh.net;

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

/**
 * TalkReceive
 * 接收线程
 * 2020/4/16 21:48
 **/
public class TalkReceive implements Runnable{
    DatagramSocket socket = null;
    private int myPort;
    private String msgFrom;

    public TalkReceive(int myPort, String msgFrom) throws SocketException {
        this.myPort = myPort;
        this.msgFrom = msgFrom;
        socket = new DatagramSocket(myPort);
    }

    @Override
    public void run() {

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

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

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

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

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

package com.mrh.net;

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;

/**
 * TalkSend
 * 发送线程
 * 2020/4/16 21:26
 **/
public class TalkSend implements Runnable{
    DatagramSocket socket = null;
    BufferedReader reader = null;

    private int myPort;
    private int toPort;
    private String toIp;

    public TalkSend(int myPort, int toPort, String toIp) throws SocketException {
        this.myPort = myPort;
        this.toPort = toPort;
        this.toIp = toIp;

        socket = new DatagramSocket(myPort);
        reader = new BufferedReader(new InputStreamReader(System.in));
    }

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

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

1.8 URL

https://www.baidu.com/

统一资源定位器:定位互联网上的某一资源

DNS域名解析：域名–>ip

1.协议：//ip：端口/项目/资源

下载网络资源

package com.mrh.net;

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

/**
 * URLDemo01
 * 下载网络资源
 * 2020/4/16 22:15
 **/
public class URLDemo01 {
    public static void main(String[] args) throws IOException {
        //1.下载地址
        URL url = new URL("https://m10.music.126.net/20200416230043/5e6b78442733cd0c96f06481229c7948/yyaac/0052/005b/020f/788cff545371798931095e7e20a8d781.m4a");

        //2.连接网络资源
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("1.m4a");

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

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

        /*System.out.println(url.getFile());
        System.out.println(url.getHost());
        System.out.println(url.getPath());
        System.out.println(url.getFile());*/

    }
}

因为我喜欢追寻过程中的自己