网络编程

概述

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. 如何准确地定位网络上的一台主机 192.168.16.124：端口，定位到这个计算机上的某个资源
2. 找到了这个主机，如何传输数据呢？

javaweb：网页编程 B/S

网络编程：TCP/IP C/S

网络通信的要素

如何实现网络的通信？

通信双方地址：

• ip 192.168.1.1
• 端口号
• 192.168.16.124:5900

规则：网络通信的协议

TCP/IP参考模型：

HTTP：超文本传输协议

FTP：文件上传协议

SMTP：发送邮件

Telnet：远程登陆

DNS：域名解析

TCP：类似于打电话；UDP：类似于发短信

小结：

1. 网络编程中有两个主要的问题
   如何准确地定位到网络上的一台或者多台主机
   • 找到主机之后如何进行通信
2. 网络编程中的要素
   IP 和 端口号 IP
   • 网络通信协议 UDP TCP
3. 万物皆对象

IP地址

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

  IP地址分类

  ipv4/ipv6

  IPV4 127.0.0.1 4个字节组成。 0~255，42亿个，2011年用尽

• IPV6 fe80::a839:ebe1:825b:2edb%5 128位，8个无符号整数！

  例如：2001:0bb2:aaaa:0015:0000:0000:1aaa:1312

import java.net.InetAddress;import java.net.UnknownHostException;//测试IPpublic 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ip地址InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");System.out.println(inetAddress2);//常用方法System.out.println(inetAddress2.getAddress());System.out.println(inetAddress2.getCanonicalHostName());//规范的名字System.out.println(inetAddress2.getHostAddress());//ipSystem.out.println(inetAddress2.getHostName());//域名，或者自己电脑的名字} catch (UnknownHostException e) {e.printStackTrace();}}}

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Ctrl+shift+Esc #打开任务管理器中的进程

import java.net.InetSocketAddress;public class TestInetSocketAddress {public static void main(String[] args) {InetSocketAddress socketAddress = new InetSocketAddress("127.0.0.1", 8080);InetSocketAddress socketAddress2 = new InetSocketAddress("localhost", 8080);System.out.println(socketAddress);System.out.println(socketAddress2);System.out.println(socketAddress.getAddress());System.out.println(socketAddress.getHostName());//地址System.out.println(socketAddress.getPort());//端口}}

通信协议

协议：

**网络通信协议：**速率，传输码率，代码结构，传输控制…

TCP/IP协议簇

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：我要断开了！B：我知道你要断开了！B：我也要跟你断开了！A：我也知道你要跟我断开了！

• 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
• 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

import java.io.IOException;import java.io.OutputStream;import java.net.InetAddress;import java.net.Socket;//客户端public class TcpClientDemo01 {public static void main(String[] args) {Socket socket = null;OutputStream os = null;//1.要知道服务器的地址try {InetAddress serverIP = InetAddress.getByName("127.0.0.1");//2.端口号int port = 9999;//3.创建一个socket连接socket = new Socket(serverIP,port);//4.发送消息    IO流os = socket.getOutputStream();os.write("你好，欢迎学习狂神说Java".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. 接受用户的消息

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.我得有一个地址serverSocket = new ServerSocket(9999);while (true){       //连续接收客户端消息//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();/*byte[] buffer = new byte[1024];int len;while ((len = is.read(buffer))!=-1){String msg = new String(buffer, 0, len);System.out.println(msg);}*///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();}}}}}

TCP文件上传

服务器端

import java.io.FileOutputStream;import java.io.InputStream;import java.io.OutputStream;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(9000);//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("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("我接收完毕了，你可以断开了".getBytes());//关闭资源fos.close();is.close();socket.close();serverSocket.close();}}

客户端

import java.io.*;import java.net.InetAddress;import java.net.Socket;public class TcpClientDemo02 {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"), 9000);//2.创建一个输出流OutputStream os = socket.getOutputStream();//3.读取文件FileInputStream fis = new FileInputStream(new File("D:\\\\environment\\\\java_project\\\\javase\\\\蜗牛.jpg"));//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，我已经结束了socket.shutdownOutput();//我已经传输完了！//确定服务器接收完毕，才能够断开连接InputStream inputStream = socket.getInputStream();//String byte[]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());//5.关闭资源baos.close();inputStream.close();fis.close();os.close();socket.close();}}

Tomcat

服务器

• 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

UDP

发短信：不用连接，需要知道对方的地址

发送端

import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;//不需要连接服务器public class UdpClientDemo01 {public static void main(String[] args) throws Exception {//1.建立一个SocketDatagramSocket 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

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();}}

发送消息

import java.io.BufferedReader;import java.io.InputStreamReader;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetSocketAddress;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.inBufferedReader 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();}}======================================================================================import java.net.DatagramPacket;import java.net.DatagramSocket;public class UdpReceiveDemo01 {public static void main(String[] args) throws Exception {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);//阻塞式接收包裹//断开连接 byebyte[] 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或接收方，实现在线交流）

import java.io.BufferedReader;import java.io.InputStreamReader;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetSocketAddress;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();}}@Overridepublic 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();}}=======================================================================================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();}}@Overridepublic 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);//阻塞式接收包裹//断开连接 byebyte[] 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();}}=====================================================================================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();}}=======================================================================================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下载网络资源

https://www.baidu.com/

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 www.baidu.com xxx.x..x..x

协议：//ip地址：端口/项目名/资源

import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;public class UrlDown {public static void main(String[] args) throws IOException {//1.下载地址URL url = new URL("https://p2.music.126.net/WqnSe7WvZOB0E_4qBsNmqw==/109951166086703110.jpg?param=50y50");//2.连接到这个资源 HTTPHttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();InputStream inputStream = urlConnection.getInputStream();FileOutputStream fos = new FileOutputStream("109951166086703110.jpg");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();}}