计算机网络

就是将地理位置不同的具有独立功能的多台计算及外部设备，通过通信线路连接起来，在网络操作系统、网络管理软件以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

目的

传播交流信息、数据交换、通信

如何做到

1.如何准确定位网络上的一台主机 192.xxx.xx.xx：端口，定位到这个计算机上的某个资源
2.找到主机，如何传输数据
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

1.ip、端口号
2.协议 tcp/ip协议
3.万物皆对象

IP

ip地址：InetAdress
唯一定位一台网络上的计算机
127.0.0.1：本机Locallost

IP地址分类

ipv4/ipv6
ipv4 127.0.0.1 4个字节 0~255 42亿 30亿在北美，4亿在亚洲，2011年用尽
ipv6：128 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：记忆ip问题

package com.xgglr;import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Arrays;public class IPDemo {public static void main(String[] args) {try {InetAddress[] inetAddresses = InetAddress.getAllByName("127.0.0.1");System.out.println(Arrays.toString(inetAddresses));InetAddress[] localHosts = InetAddress.getAllByName("localhost");System.out.println(Arrays.toString(localHosts));InetAddress localHost = InetAddress.getLocalHost();System.out.println(localHost);InetAddress[] baiduName = InetAddress.getAllByName("www.baidu.com");System.out.println(Arrays.toString(baiduName));for (InetAddress address : baiduName) {String canonicalHostName = address.getCanonicalHostName();//规范名称String hostName = address.getHostName();//域名String hostAddress = address.getHostAddress();//IPSystem.out.println(canonicalHostName);System.out.println(hostName);System.out.println(hostAddress);System.out.println("============");}} catch (UnknownHostException e) {e.printStackTrace();}}
}

端口

表示计算机上的一个程序的进程，不同的进程端口号不同，区分如软件
被规定0~65535
tcp/udp 6553582 tcp:80 udp:80 单个协议下，端口号不能冲突
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 “5900” 查看指定端口
tasklist|findstr “8696” 查看指定端口的进程

通信协议

网络通信协议：速率，传输码率，代码结构，传输控制
分层思想
tcp/ip协议：一组协议
tcp：用户传输协议，udp：用户数据报协议
出名的协议：tcp，ip：网络互联协议

tcp和udp对比

tcp：打电话
连接 稳定
三次握手 四次挥手
客户端 服务端
传输完程 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
不能有没有准备好 都可以发送

TCP

客户端：连接服务器Socket，发送消息

package com.xgglr.tcpDemo;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 tcpClintDemo {public static void main(String[] args) {try {InetAddress byName = InetAddress.getByName("localhost");int port = 8888;Socket socket = new Socket(byName,port);OutputStream outputStream = socket.getOutputStream();outputStream.write("您好!!!，这里时客户端".getBytes());outputStream.close();socket.close();} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}
}

服务端：建立服务的接口ServerSocket，等待用户的连接accept，接受用户的消息

package com.xgglr.tcpDemo;import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Arrays;//服务端
public class tcpServerDemo {public static void main(String[] args) {ServerSocket serverSocket = null;Socket socket = null;InputStream inputStream = null;ByteArrayOutputStream byteArrayOutputStream = null;try {serverSocket = new ServerSocket(8888);while (true){socket = serverSocket.accept();inputStream = socket.getInputStream();//管道流byteArrayOutputStream = new ByteArrayOutputStream();byte[] bytes = new byte[1024];int len;while ((len = inputStream.read(bytes)) != -1){byteArrayOutputStream.write(bytes,0,len);}System.out.println(byteArrayOutputStream.toString());}} catch (IOException e) {e.printStackTrace();}finally {if (byteArrayOutputStream != null){try {byteArrayOutputStream.close();} catch (IOException e) {e.printStackTrace();}}if (inputStream != null){try {inputStream.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.xgglr.tcpDemo;import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
//服务端
public class TcpFileDownLoaderServerDemo {public static void main(String[] args) {try {while (true){ServerSocket socket = new ServerSocket(9999);Socket accept = socket.accept();InputStream is = accept.getInputStream();FileOutputStream fos = new FileOutputStream(new File("D:\\software\\JavaCode\\javaSE\\JavaSE01\\src\\com\\xgglr\\tcpDemo\\tcp.jpg"));byte[] buffer = new byte[1024];int len;while ((len = is.read(buffer)) != -1){fos.write(buffer,0,len);}//确认接收到了，可以断开accept.getOutputStream().write("已经接收，可以关闭！！！".getBytes());fos.close();is.close();accept.close();socket.close();}} catch (IOException e) {e.printStackTrace();}}
}

package com.xgglr.tcpDemo;import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
//客户端
public class TcpFileDownLoaderClintDemo {public static void main(String[] args) {try {//创建连接InetAddress byName = InetAddress.getByName("localhost");int port = 9999;Socket socket = new Socket(byName,port);//创建输出流OutputStream os = socket.getOutputStream();//读取文件FileInputStream fileInputStream = new FileInputStream(new File("2.jpg"));//写出文件byte[] buffer = new byte[1024];int len;while ((len = fileInputStream.read(buffer)) != -1){os.write(buffer,0,len);}//通知服务器发送完毕socket.shutdownOutput();//确认是否接收InputStream is = socket.getInputStream();//管道流ByteArrayOutputStream baos = new ByteArrayOutputStream();byte[] bytes = new byte[1024];int lens;while ((lens = is.read(bytes)) != -1){baos.write(bytes,0,lens);}System.out.println(baos.toString());fileInputStream.close();os.close();socket.close();} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}
}

UDP

不用连接，需要知道地址

package com.xgglr.udp;import java.io.IOException;
import java.net.*;
//UDP客户端
public class UdpClint {public static void main(String[] args) {//建立连接Sockettry {DatagramSocket socket = new DatagramSocket();//建包String msg = "你好！！！ Server";InetAddress localhost = InetAddress.getByName("localhost");int port = 9090;/*** byte buf[], 数据* int offset, 数据的起始长度* int length, 结束长度* netAddress address, 接受ip* int port 端口号* */DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);//发送包socket.send(packet);socket.close();} catch (SocketException e) {e.printStackTrace();} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}
}

package com.xgglr.udp;import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.Arrays;//UDP服务端
public class UdpServer {public static void main(String[] args) {//开放端口try {DatagramSocket socket = new DatagramSocket(9090);//接受数据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().getHostName());System.out.println(packet.getPort());System.out.println(packet.getLength());// System.out.println(Arrays.toString(packet.getData()));socket.close();} catch (SocketException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}
}