Network programming knowledge summary

network programming

1 Overview

computer network:

Computer network refers to the geographical positions different independent function having a plurality of computers and peripheral equipment, connected via a communication line, the network operating system , network management software and a network communication protocol under the management and coordination, to achieve the sharing of resources and information computer system delivery.

Network programming purposes:

Unlimited radio stations, the spread of information exchange, data exchange, communication ......

What I want to achieve the desired effect:

1. A host ip address on how to accurately locate network: port, navigate to a resource on this computer
2. I found the host, how to transfer data?

Concept B / S and C /:

javaweb: web programming B / S

Network Programming: TCP / IP C / S

2, the elements of the communication network

How to achieve communication network?

Communication between the two sides address:

• ip: port

Rules: network communication protocol

TCP / IP reference model:

summary:

1. Network Programming with two main issues:
   • How accurate positioning on the network to one or multiple hosts
   • After finding how to communicate with the host
2. Network Programming elements:
   • IP port number and IP
   • Network communication protocol UDP, TCP
3. Everything Is an Object:
   • There must communicate with the network-related classes in java
   • No classes need to be related to define your own

3、IP

ip address: InetAdress

• The only locate computers on a network

• 127.0.0.1: local address i.e. localhost

• Classification ip address

  • ipv4/ipv6

    • IPV4: 4 bytes. About 42 million in North America accounted for 30 billion and 400 million in Asia in 2011, has been used up

    • IPV6: 12 bits. 8 unsigned integer, e.g.

      1111:2222:3333:4444:5555:6666:aaaa:cccc

  • Public network (Internet) and private (local area network)

    • ABCD class address
    • 192.1688.xx.xx, specifically for use within the organization

• Domain Name: Memory IP

  • IP: www.jd.com (self-purchase)

Test code:

package pers.mobian.tcpip;

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

public class TestMyip {
    public static void main(String[] args) throws UnknownHostException {
        //查询本机地址
        InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
        InetAddress inetAddress2 = InetAddress.getByName("localhost");
        InetAddress inetAddress3 = InetAddress.getLocalHost();
        System.out.println(inetAddress1);
        System.out.println(inetAddress2);
        System.out.println(inetAddress3);

        //查询网络ip地址
        InetAddress inetAddress4 = InetAddress.getByName("www.baidu.com");
        System.out.println(inetAddress4);

        //常用的方法
        System.out.println(inetAddress4.getCanonicalHostName());//规范的名字
        System.out.println(inetAddress4.getHostAddress());//ip
        System.out.println(inetAddress4.getHostName());//域名或者自己电脑的名字

    }
}

Results of the:

/127.0.0.1
localhost/127.0.0.1
DESKTOP-EGA979M/192.168.253.1
www.baidu.com/183.232.231.174
183.232.231.174
183.232.231.174
www.baidu.com

4, Port

Port process represents a program on the computer

• Ports have different software used to distinguish

• Port predetermined range: 0 to 65535

• TCP and UDP respectively occupy 65,535, that is the total number of computer port 65535 * 2

• Port Classification

  • Public ports 0 to 1023

    • HTTP : 80
    • HTTPS : 443
    • FTP : 21
    • Telent : 23

  • Program Port Register: 1024 to 49151, or assign the user program

    • Tomcat：8080
    • MySQL：3306
    • Oracle：1521

  • Dynamic private: 49152 to 65535

    netstat -ano //查看所有的端口
    netstat -ano |findstr “端口号” //查看指定的端口号
    tasklist|findstr "端口号"  //查看指定端口号的进程 

Test code:

package pers.mobian.socket;

import java.net.InetSocketAddress;

public class TestSocket02 {
    public static void main(String[] args) {
        InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1",8080);
        InetSocketAddress inetSocketAddress2 = new InetSocketAddress("localhost",8080);

        System.out.println(inetSocketAddress);
        System.out.println(inetSocketAddress2);

        System.out.println(inetSocketAddress.getAddress());//获取地址
        System.out.println(inetSocketAddress.getHostName());//获取主机名字
        System.out.println(inetSocketAddress.getPort());//获取端口

    }
}

Results of the:

/127.0.0.1:8080
localhost/127.0.0.1:8080
/127.0.0.1
127.0.0.1
8080

5, the communication protocol

Network communication protocol: rate, transmission rate, code structure, the transmission control ......

TCP / IP protocol suite: is a set of protocols

• TCP: User Transfer Protocol
• UDP: User Datagram Protocol
• IP: Internet Protocol

TCP and UDP comparison:

TCP: call

• Stable connection

• Three-way handshake, waving four

  //最少需要三次，保证稳定连接！<连接>
  A：你瞅啥？
  B：瞅你咋地？
  A：干一场
  
  
  //四次挥手 <断开>
  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

• Client, server

• The transfer is complete, releases the connection, inefficiency

UDP: texting

• Not connected, unstable
• Client, server: no clear boundaries
• With or without ready, you can send it to you
• DDOS: flood attack (send large amounts of information, port congestion, saturation attack)

6、TCP

1. Text Transfer

The client test code:

package pers.mobian.socket;

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 TestClientSocket {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            //1、要知道服务器得地址、端口号
            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IO流信息
            os = socket.getOutputStream();
            os.write("你好，默辨".getBytes());


        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            
            //关闭资源，对关闭得资源进行一个判定，如果没有开启则不需要关闭
            if(os!=null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

Server test code:

package pers.mobian.socket;

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

//服务器端
public class TestServersSocket {
    public static void main(String[] args) throws Exception {
        //1、给自己新建一个端口号
        ServerSocket serverSocket = new ServerSocket(9999);
        //2、等待客户端进行连接
        Socket socket = serverSocket.accept();
        //3、读取客户端的消息
        InputStream inputStream = socket.getInputStream();

        //4、管道流
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer))!= -1){
            baos.write(buffer,0,len);
        }
        System.out.println(baos.toString());

        //5、关闭资源（后开先关）
        baos.close();
        inputStream.close();
        socket.close();
        serverSocket.close();

    }
}

Results of the:

//服务器端显示
你好，默辨

2. File Upload

Test code:

//服务器
package pers.mobian.socket;

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

public class TestServersSocket2 {
    public static void main(String[] args) throws Exception {
        //1、创建服务
        ServerSocket serverSocket = new ServerSocket(9999);
        //2、监听客户端得连接
        Socket socket = serverSocket.accept();//阻塞式监听，会一直等待
        //3、获取输入流
        InputStream is = socket.getInputStream();
        //4、文件输出
        FileOutputStream fos = new FileOutputStream(new File("E:\\ideaWorkSpace\\pan\\day14_socket_01\\33.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = is.read(buffer)) != -1) {
            fos.write(buffer,0,len);
        }

        //5、通知客户端，我接受完毕了
        OutputStream os = socket.getOutputStream();
        os.write("我接受完了".getBytes());
        //6、关闭资源
        fos.close();
        is.close();
        socket.close();

    }
}

//客户端
package pers.mobian.socket;

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

public class TestClientSocket2 {
    public static void main(String[] args) throws Exception {
        //1、创建一个Socket连接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9999);
        //2、创建一个输出流
        OutputStream os = socket.getOutputStream();
        //3、读取文件
        FileInputStream fis = new FileInputStream(new File("E:\\ideaWorkSpace\\pan\\day14_socket_01\\3.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、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(buffer2,0,len2);
        }
        System.out.println(baos.toString());

        //6、关闭资源
        fis.close();
        os.close();
        os.close();
        socket.close();
    }
}

7、Tomcat

Server;

• Custom S
• Tomcat server S

Client:

• Custom C
• Browser B

8、UDP

UDP does not have the concept of server-side and client, only the sender and receiver have the concept

1. Case I: A simple message

Sending end test code:

package pers.mobian.socket;

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

//发送端
public class TestClientSocket3 {
    public static void main(String[] args) throws Exception {
        //1、建立一个Socket
        DatagramSocket socket = new DatagramSocket();

        //2、建包
        String msg = "你好";
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;

        //参数得列表分别是：数据，数据长度始，数据长度终，地址，端口号
        DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);

        //3、发送包
        socket.send(packet);
        //4、关闭资源
        socket.close();
    }
}

Test code receiving end:

package pers.mobian.socket;

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

//接收端
public class TestServersSocket3 {
    public static void main(String[] args) throws Exception {
        //1、设置开放端口
        DatagramSocket socket = new DatagramSocket(9090);

        //2、准备接受数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
        socket.receive(packet);

        System.out.println(packet.getAddress().getHostAddress());
        //3、将需要打印得数据进行格式转换
        System.out.println(new String(packet.getData(),0,packet.getLength()));

        socket.close();

    }
}

2. Case I: a simple chat realization

Sending end test code:

package pers.mobian.udp;

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

public class TestUDPSender {
    public static void main(String[] args) throws Exception {
        //设置开放端口
        DatagramSocket socket = new DatagramSocket(8888);

        while (true) {
            //1、读取控制台的数据
            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            //2、将控制台的一行语句赋值给data
            String data = reader.readLine();
            //3、将data包装成数据
            byte[] datas = data.getBytes();
            //4、将数据打包成package
            DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress("localhost", 6666));
            //5、发送信息
            socket.send(packet);

            //判定的数据输入应为最初的输入数据，而非包装后的数据
            if(data.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

Test code receiving end:

package pers.mobian.udp;

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

public class TestUDPReceiver {
    public static void main(String[] args) throws Exception {
        //设置开放端口
        DatagramSocket socket = new DatagramSocket(6666);
        while (true) {

            //1、准备接受包裹
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container, 0, container.length);
            socket.receive(packet);
            //2、打印接受到的数据
            System.out.println(new String(packet.getData(),0,packet.getLength()));
            //设置断开连接
            byte[] data = packet.getData();
            String receiverData = new String(data, 0, data.length);

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

3. Using multithreading chat

Sender test code:

package pers.mobian.udp;

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

public class TestUDPSender2 implements Runnable {
    private int fromPort;
    private String toIP;
    private int toPort;
    DatagramSocket socket = null;
    BufferedReader reader = null;

    public TestUDPSender2(int fromPort, String toIP, int toPort) {
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;

        try {
            //设置开放端口
            socket = new DatagramSocket(fromPort);
            //1、读取控制台的数据
            reader = new BufferedReader(new InputStreamReader(System.in));


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

    @Override
    public void run() {
        while (true) {
            try {
                //2、将控制台的一行语句赋值给data
                String data = reader.readLine();
                //3、将data包装成数据
                byte[] datas = data.getBytes();
                //4、将数据打包成package
                DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress(this.toIP, this.toPort));
                //5、发送信息
                socket.send(packet);

                //判定的数据输入应为最初的输入数据，而非包装后的数据
                if (data.equals("bye")) {
                    break;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

Receiver test code:

package pers.mobian.udp;

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

public class TestUDPReceiver2 implements Runnable {

    DatagramSocket socket = null;
    private int port;
    private String msgFrom;

    public TestUDPReceiver2(int port, String msgFrom) {
        this.port = port;
        this.msgFrom = msgFrom;

        try {
            //设置开放端口
            socket = new DatagramSocket(port);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println(88888);
        }
    }

    @Override
    public void run() {

        while (true) {

                //1、准备接受包裹
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
            try {
                socket.receive(packet);//阻塞式接受
            } catch (IOException e) {
                e.printStackTrace();
                System.out.println("111");
            }
            //2、打印接受到的数据

                //设置断开连接
                byte[] data = packet.getData();
                String receiverData = new String(data, 0, data.length);

                System.out.println(msgFrom + " : " + receiverData);
                if (receiverData.equals("bye")) {
                    break;
                }
        }
        socket.close();
    }
}

Test code:

package pers.mobian.udp;

public class TestUDPReceiver2Main1 {
    public static void main(String[] args) {
        new Thread(new TestUDPSender2(7777,"localhost",9999)).start();
        new Thread(new TestUDPReceiver2(8888,"老师")).start();
    }
}

Test code:

package pers.mobian.udp;

public class TestUDPReceiver2Main2 {
    public static void main(String[] args) {
        new Thread(new TestUDPSender2(5555,"localhost",8888)).start();
        new Thread(new TestUDPReceiver2(9999,"学生")).start();
    }
}

Results of the:

//Main1
ni
学生 : jj
 
//Main2
老师 : ni                                                                                 
jj

Class 4. url

URL category of use:

Test code:

package pers.mobian.udp;

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

public class TestURL {
    public static void main(String[] args) throws MalformedURLException {
        URL url = new URL("http://localhost:8080/mobian/index.jsp?username=mobian&password=123");
        System.out.println(url.getProtocol());//使用的协议
        System.out.println(url.getHost());//主机IP
        System.out.println(url.getPort());//使用的端口号
        System.out.println(url.getPath());//文件路径
        System.out.println(url.getFile());//文件的全路径
        System.out.println(url.getQuery());//参数列表
    }
}

Results of the:

http
localhost
8080
/mobian/index.jsp
/mobian/index.jsp?username=mobian&password=123
username=mobian&password=123

The use of network resources url path to download the test code:

package pers.mobian.udp;


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

public class TestDownURL {
    public static void main(String[] args) throws IOException {
        //1、请求下载的地址
        URL url = new URL("https://m701.music.126.net/20200121172558/e95dfac9e276e6d145b5f2638a036c2b/jdyyaac/035e/565f/055f/447bb91679a53ba93bc2258f72f57669.m4a");

        //2、连接到这个资源HTTP
        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("77.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();
    }
}