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网络编程

网友: 文档中心 2022-05-27 22:15:31

网络编程

  • 计算机网络：

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。

  • 网络编程的目的：

无线电台…传播交流信息，数据交换。通信

  • 想要达到这个效果需要什么：
  1. 如何准确的定位网络上的一台主机，端口，定位到这个计算机上的某个资源
  2. 找到了这个主机，如何传输数据？

javaweb： 网页编程 B/S

网络编程： TCP/IP C/S

  1. 网络编程中有两个主要问题
  • 如何准确的定位网络上的一台主机，端口，定位到这个计算机上的某个资源
  • 找到了这个主机，如何传输数据？
  1. 网络编程中的要素
  • IP和端口号
  • 网络通信协议

IP

ip地址：InetAddress

  • 唯一定位一台网络上计算机
  • 127.0.0.1 ： localhost
  • ip地址的分类
    • IPV4 127.0.0.1 ,4个字节组成
    • 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
package com.company.lesson01;import java.net.InetAddress;import java.net.UnknownHostException;public class TestInetAddress {    public static void main(String[] args) { try {     //查询本机地址     InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");     System.out.println(inetAddress1);     InetAddress inetAddress3 = InetAddress.getByName("localhost");     System.out.println(inetAddress3);     InetAddress inetAddress4 = InetAddress.getLocalHost();     System.out.println(inetAddress4);     //查询网站地址     InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");     System.out.println(inetAddress2); } 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
  • 端口分类
    • 共有端口：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

InetSocketAddress inetSocketAddress1 = new InetSocketAddress("127.0.0.1", 8080);System.out.println(inetSocketAddress2.getHostName());

通信协议

网络通信协议：速率、传输码率、代码结构、传输控制…

TCP/IP协议 （实际上是一组协议）

  • TCP ：用户传输协议 （好比打电话）
    • 连接，稳定
    • 三次握手，四次挥手
    • 客户端，服务端
    • 传输完成，释放连接，效率低
  • UDP ：用户数据报协议 （好比发短信）
    • 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，都可以打给你…
    • 导弹
    • DDOS ：洪水攻击（饱和攻击）

TCP

客户端

  1. 连接服务器 Socket
  2. 发送消息
package com.company.lesson02;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 TcpClientDemo01 {    public static void main(String[] args) { Socket socket = null; OutputStream os = null; try {     //1.要知道服务器地址,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.发送消息 IO流     os = socket.getOutputStream();     os.write("欢迎,yang".getBytes()); } 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();  }     } }    }}

服务器

  1. 建立服务的端口 ServerSocket
  2. 等待用户的连接 accept
  3. 接收用的消息
package com.company.lesson02;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.ServerSocket;import java.net.Socket;//服务端public class TcpServerDemo01 {    public static void main(String[] args) { ServerSocket serverSocket = null; Socket socket = null; InputStream is = null; ByteArrayOutputStream baos = null; try {     //1.得有一个地址     serverSocket = new ServerSocket(9999);     //2.等待客户端连接过来     socket = serverSocket.accept();     //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 {     //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();  }     } }    }}

文件上传

服务器端

package com.company.lesson02;import java.io.*;import java.net.ServerSocket;import java.net.Socket;public class TcpServerDemo02 {    public static void main(String[] args) throws Exception { //1.创建服务 ServerSocket serverSocket = new ServerSocket(9999); //2.监听客户端的连接 Socket socket = serverSocket.accept();  //阻塞式监听，会一直等待客户端连接 //3.获取输入流 InputStream is = socket.getInputStream(); //4.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); } //通知客户端我接收完毕了 OutputStream os = socket.getOutputStream(); os.write("finsish".getBytes()); fos.close(); is.close(); socket.close(); serverSocket.close();    }}

客户端

package com.company.lesson02;import java.io.*;import java.net.InetAddress;import java.net.Socket;import java.net.UnknownHostException;public class TcpClientDemo02 {    public static void main(String[] args) throws Exception { //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("微信截图_20210315183342.png")); //4.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，发送完了 socket.shutdownOutput();//我已传输完了 //确定服务器接收完毕，才能够断开连接 InputStream inputStream = socket.getInputStream(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); byte[] buffer2 = new byte[2014]; int len2; while ((len2=inputStream.read(buffer2))!=-1){     baos.write(buffer2,0,len2); } System.out.println(baos.toString()); //5.关闭资源 baos.close(); inputStream.close(); fis.close(); os.close(); socket.close();    }}

Tomcat

服务端

  • 自定义 S
  • Tomcat服务器 S

客户端

  • 自定义 C
  • 浏览器 B

UDP

发送消息

发送端

package com.company.lesson03;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;import java.net.SocketException;//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 = "Hello!"; //发送给谁 InetAddress localhost = InetAddress.getByName("localhost"); int port = 9090; //数据，数据的长度起始，要发给谁 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.company.lesson03;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.SocketException;//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);//接收 socket.receive(packet); System.out.println(packet.getAddress().getHostAddress()); System.out.println(new String(packet.getData(),0,packet.getLength())); //关闭连接 socket.close();    }}

UDP实现聊天

Sender

package com.company.chat;import java.io.BufferedReader;import java.io.InputStreamReader;import java.net.*;public class UdpSenderDemo01 {    public static void main(String[] args) throws Exception { DatagramSocket socket = new DatagramSocket(8888); //准备数据，从控制台读取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();    }}

Receive

package com.company.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);     //阻塞式接收包裹     socket.receive(packet);     //断开连接 bye     byte[] data = packet.getData();     String receiveDatas = new String(data, 0, data.length);     System.out.println(receiveDatas);     if (receiveDatas.equals("bye")){  break;     } } socket.close();    }}

UDP多线程在线咨询

TalkSend

package com.company.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 (SocketException e) {     e.printStackTrace(); }    }    @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 (data.equals("bye")){      break;  }     } catch (Exception e) {  e.printStackTrace();     } } socket.close();    }}

TalkReceive

package com.company.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);      //阻塞式接收包裹      socket.receive(packet);      //断开连接 bye      byte[] data = packet.getData();      String receiveDatas = new String(data, 0, data.length);      System.out.println(msgFrom + ":" + receiveDatas);      if (receiveDatas.equals("bye")) {   break;      }  } catch (IOException e) {      e.printStackTrace();  }     } socket.close();    }}

TalkStudent

package com.company.chat;public class TalkStudent {    public static void main(String[] args) { new Thread(new TalkSend(7777,"Localhost",9999)).start(); new Thread(new TalkReceive(8888,"老师")).start();    }}

TalkTeacher

package com.company.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();    }}

URL

统一资源定位符：定位互联网上的某一个资源

DNS域名解析： www.bilibili.com —> xxx.xxx.xxx.xxx

协议：//ip地址：//端口/项目名/资源
package com.company.lesson04;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStream;import java.net.*;public class URlDown {    public static void main(String[] args) throws Exception { //下载地址 URL url = new URL("https://p2.music.126.net/0O1DSaOFQDa0XAL1oxBDfg==/109951165325140747.jpg?param=120y120"); //连接到这个资源 HTTP HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); //下载 InputStream inputStream = urlConnection.getInputStream(); FileOutputStream fos = new FileOutputStream("109951165325140747.jpg"); byte[] buffer = new byte[1024]; int len; while ((len=inputStream.read(buffer))!=-1){     fos.write(buffer,0,len); } fos.close(); inputStream.close(); urlConnection.disconnect();    }}
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