笔记11：网络编程

网络编程

概述

计算机网络是指将地理位置不同的具有独立功能的多台计算机及其外部设备，通过通信线路连接起来，在网络操作系统，网络管理软件及网络通信协议的管理和协调下，实现资源共享和信息传递的计算机系统

网络通信的要素

通信双方地址：

• IP
• 端口号

规则：网络通信的协议

• TCP
• UDP

TCP/IP参考模型

IP

ip地址：InetAddress

• 唯一定位一台网络上的计算机
• 127.0.0.1：本机 localhost
• ip地址的分类
  • IPV4/IPV6
    • IPV4 如127.0.0.1 4个字节组成 ，每个0~255
    • IPV6 128位 8个无符号整数
  • 公网（互联网）-私网（局域网）
    • ABCD类地址
    • 192.168.xx.xx专门给组织内部使用的

• 域名：

package com.wang.netcode;

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

public class Demo01 {
    public static void main(String[] args) {
        try {
            //查询本机地址
            InetAddress byName = InetAddress.getByName("127.0.0.1");
            System.out.println(byName);
            InetAddress localHost = InetAddress.getLocalHost();
            System.out.println(localHost);
            //查询网站IP地址
            InetAddress byName1 = InetAddress.getByName("www.baidu.com");
            System.out.println(byName1);
            // 常用方法
            System.out.println(byName1.getAddress());
            System.out.println(byName1.getCanonicalHostName()); // 规范的名字
            System.out.println(byName1.getHostAddress()); // 获得主机地址
            System.out.println(byName1.getHostName()); // 获得电脑名字
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

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
• TCP,UDP:65535*2 tcp:80 ,udp:80 ,单个协议下，端口号不能冲突
• 端口的分类
  • 公有端口0-1023（尽量不要使用，一般内置进程使用)
    • Http:80
    • Https:443
    • Ftp:21
    • Telnet:23
    • 远程连接：22
  • 程序注册端口：1024-49151，分配给用户或者程序
    • Tomcat：8080
    • MySql：3306
    • Oracle：1521
  • 动态，私有：49152-65535

netstat -ano # 查看所有端口

netstat -ano|findstr "端口号"  # 查看指定的端口

tasklist|findstr "8696"  # 查看指定端口的进程

通信协议

协议：约定，就好比我们说的普通话

网络通信协议：速率，传输码率，代码结构，传输控制…

TCP/IP协议簇，实际上是一组协议
参考百度百科：
https://baike.baidu.com/item/TCP/IP协议/212915

重要：

• TCP：用户传输协议
• UDP：用户数据报协议

TCP的三次握手和四次挥手

最少需要三次，保证稳定连接
A:你愁啥？
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！

可以理解为TCP就像是连接打电话，要确定对方能收到消息。UDP就像是不连接发短信，短信发出去了，但不确定对方能不能收得到。

TCP

• 客户端
  • 连接服务器 通过Socket
  • 发送消息
• 服务端
  • 建立服务的端口ServerSocket
  • 等待用户的连接 accept
  • 接收用户的消息

package com.wang.netcode;

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

public class TcpClientDemo01 {
    // 客户端
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            // 1.要知道服务器的地址,端口
            InetAddress serverIp = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            // 2.创建一个Socket连接
            socket = new Socket(serverIp, port);
            // 3.发送消息，IO流
            os = socket.getOutputStream();
            String string = "我在学习网络编程...";
            os.write(string.getBytes()); // 将字符串打散为字节数组
        } catch (Exception 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();
                }
            }
        }
    }
}

package com.wang.netcode;

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

public class TcpServerDemo01 {
// 服务端
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            // 1.我得有一个地址
            serverSocket = new ServerSocket(9999);
            while (true) {
                // 2.等待客户端连接  循环监听
                socket = serverSocket.accept();// accept(); 监听
                // 3.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 {
            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();
                }
            }
        }
    }
}

• 文件上传

package com.wang.netcode;

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

public class TcpClientDemo02 {
    // 客户端
    public static void main(String[] args) throws Exception {
        // 1.创建一个Socket连接
        InetAddress serverIp = InetAddress.getByName("127.0.0.1");
        int port = 9000;
        Socket socket = new Socket(serverIp,port);
        // 2.创建一个输出流
        OutputStream os = socket.getOutputStream();
        // 3.文件流  读取文件
        FileInputStream fis = new FileInputStream(new File("avatar.jpg"));
        // 4.写出文件
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1){
            os.write(buffer,0,len);
        }
        // 5.通知服务器，文件写出结束了
        socket.shutdownOutput();
        // 6.服务器确定接收后断开服务
        InputStream is = socket.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer2 = new byte[1024];
        int len2;
        while ((len2=is.read(buffer2))!=-1){
            baos.write(buffer2,0,len2);
        }
        System.out.println(baos.toString());
        // 7.关闭资源
        baos.close();
        fis.close();
        os.close();
        is.close();
        socket.close();
    }
}

package com.wang.netcode;

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

public class TcpServerDemo02 {
    //服务端
    public static void main(String[] args) throws Exception {
        // 1.创建服务
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        FileOutputStream fos = null;
        serverSocket = new ServerSocket(9000);
        // 2.监听客户端的连接
        socket = serverSocket.accept();// 阻断式监听，会一直等待客户端连接
        // 3.获取输入流
        is = socket.getInputStream();
        // 4.文件输出
        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);
        }
        System.out.println("成功接收...");
        // 5.通知客户端接收完毕
        OutputStream os = socket.getOutputStream();
        os.write("我接收到了，你可以关闭了...".getBytes());
        // 6.关闭资源
        fos.close();
        ((OutputStream) os).close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}

UDP

发短信：不用连接，但是要知道对方的地址

发送端：

package com.wang.netcode;

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

//不需要连接服务器
public class UdpClientDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立一个Socket
        DatagramSocket socket = new DatagramSocket();

        //2.建个包
        String msg = "你好啊，服务器！";

        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;

        //数据，数据的长度起始，要发送给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);

        //3.发送包
        socket.send(packet);

        //4.关闭流
        socket.close();
    }
}

接收端:

package com.wang.netcode;

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 Exception{
        //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);//阻塞接收

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

        //关闭连接
        socket.close();
    }
}

• 聊天案例

发送方：

package com.wang.netcode.chat;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;
import java.nio.charset.StandardCharsets;

public class UdpSenderDemo01 {
    public static void main(String[] args) throws Exception {
        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：

package com.wang.netcode.chat;

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

public class UdpReceiveDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);

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

            //断开连接 bye
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, packet.getLength());
            System.out.println(receiveData);
            if (receiveData.equals("bye")){
                break;
            }
        }
        socket.close();
    }

}

UDP多线程在线咨询：两人都可以是发送方，也都可以是接收方

package com.wang.netcode.chat;

public class TalkStudent {
    public static void main(String[] args) throws Exception {
        //开启两个线程
        new Thread(new TalkSend(7777,"localhost",9999)).start();
        new Thread(new TalkReceive(8888,"老师")).start();
    }
}

package com.wang.netcode.chat;

public class TalkTeacher {
    public static void main(String[] args) throws Exception {
        new Thread(new TalkSend(5555,"localhost",8888)).start();
        new Thread(new TalkReceive(9999,"学生")).start();
    }
}

package com.wang.netcode.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) throws Exception {
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;

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

    @Override
    public void run() {

        while (true) {
            String data = null;
            try {
                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 (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

package com.wang.netcode.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.port = port;
        this.msgFrom = msgFrom;
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {

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

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

URL

统一资源定位符：定位互联网上的某一个资源

• 网络资源下载

协议://ip地址:端口/项目名/资源  # http://127.0.0.1:8080/wang/Security.txt

package com.wang.netcode;

import java.net.MalformedURLException;
import java.net.URL;

public class UrlDemo01 {
    public static void main(String[] args) throws MalformedURLException {
        URL url = new URL("http://localhost:8080/helloword/index.jsp?username=wang&password=123");
        System.out.println(url.getProtocol());//协议
        System.out.println(url.getHost());//主机ip
        System.out.println(url.getPort());//端口
        System.out.println(url.getPath());//文件
        System.out.println(url.getFile());//全路径
        System.out.println(url.getQuery());//参数
    }
}

从网络上下载资源

package com.wang.netcode;

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

public class UrlDown {
    public static void main(String[] args) throws Exception {
        //1.下载地址
        URL url = new URL("http://localhost:8080/wang/Security.txt");

        //2.连接到这个资源 HTTP
        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("Security.txt");
        byte[] buffer = new byte[1024];
        int len;
        while ((len=inputStream.read(buffer))!=-1) {
            fos.write(buffer,0, len);//写出这个数据
        }
        fos.close();
        inputStream.close();
        urlConnection.disconnect();//断开连接
    }
}