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三要素之一 IP地址
A类中:
(1) 10.X.X.X是私有地址(私有地址就是在互联网上不使用)
(2) 127.X.X.X 是保留地址
A类 中国只有三个 政府 电信 军事部门,大多都在美国
B类中:
(1) 172.16.0.0 --- 172.31.255.255是私有地址
(2) 169.254.X.X 是保留地址
B类 一般为大学的校园网
C类中:
192.168.X.X 是私有地址
我们一般用C类
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两个相关的DOS命令:
ipconfig 查看本机ip地址
ping 后面跟ip地址,测试本机与指定ip地址间的通信是否有问题
特殊的IP地址:
127.0.0.1 回环地址(表示本机)
X.X.X.255 广播地址
X.X.X.0 网络地址
三要素之二 端口号
三要素之三 协议
通信的规则
三次握手协议TCP
A: 发送请求 B: 回复同意 A:发送
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UDP协议发送协议
A:创建发送方的Socket对象
B:创建数据,并把数据打包
C:调用Socket对象发送方法发送数据
D:释放资源
package cn.itcast_02; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; public class SendDemo { public static void main(String[] args) throws IOException { //Socket sk = new Socket(); DatagramSocket ds = new DatagramSocket(); //创建数据包 //发送数据包 //public void send(DatagramPacket p); byte[] bys = "hello,udp,我来啦。".getBytes(); int length = bys.length; InetAddress address = InetAddress.getByName("DESKTOP-0257CLH"); int port = 10086; //DatagramSocket(byte[] buf,int length, InetAddress address,int port) DatagramPacket dp = new DatagramPacket(bys,length,address,port); ds.send(dp); //释放资源 ds.close(); } }
UDP协议接收协议
A:创建发送方的Socket对象
B:创建一个数据包(接受容器)
C:调用Socket对象接收方法接收数据
D:解析数据包,并显示在控制台
E:释放资源
package cn.itcast_02; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; import java.net.SocketException; public class receiveDemo { public static void main(String[] args) throws IOException { //创建Socket对象 //带参构造 DatagramSocket(int port) DatagramSocket ds = new DatagramSocket(10086); //创建一个数据包来接收对象 //DatagramPacket(byte[] buf, int length) byte[] bys = new byte[1024]; int length = bys.length; DatagramPacket dp = new DatagramPacket(bys,length); //调用Socket对象的接收方法来接收数据 // public void receive(DatagramPacket p) ds.receive(dp); //解析数据包,显示在控制台 //获取对方的ip InetAddress address = dp.getAddress(); String ip = address.getHostAddress(); //public byte[] getData():获取数据缓冲区 byte[] bys2 = dp.getData(); //public int getLength():获取数据的实际长度 int len = dp.getLength(); String s = new String(bys2,0,len); System.out.println(ip+"传递的数据是:"+s); //释放资源 ds.close(); } }
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图解
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主程序:
package cn.itcast_03; import java.io.IOException; import java.net.DatagramSocket; import java.net.SocketException; /* * 通过多线程改进改才的方法,这样就可以实现在在一个窗口发送和接收数据了 * * */ public class ChatRoom { public static void main(String[] args) throws IOException { DatagramSocket dsSend = new DatagramSocket(); DatagramSocket dsReceive = new DatagramSocket(12306); SendThread st = new SendThread(dsSend); ReceiveThread rt = new ReceiveThread(dsReceive); Thread t1 = new Thread(st); Thread t2 = new Thread(rt); t1.start(); t2.start(); } }
发送方:
package cn.itcast_03; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; public class SendThread implements Runnable { private DatagramSocket ds; public SendThread(DatagramSocket ds) { this.ds = ds; } @Override public void run() { try { // 封装键盘录入数据 BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String line = null; while ((line = br.readLine()) != null) { byte[] bys = line.getBytes(); // 创建数据包 // 发送数据包 // public void send(DatagramPacket p); // byte[] bys = "hello,udp,我来啦。".getBytes(); // int length = bys.length; // InetAddress address = InetAddress.getByName("DESKTOP-0257CLH"); // int port = 10086; // DatagramPacket(byte[] buf,int length, InetAddress address,int port) // DatagramPacket dp = new DatagramPacket(bys,length,address,port); DatagramPacket dp = new DatagramPacket(bys, bys.length, InetAddress.getByName("DESKTOP-0257CLH"), 12306); ds.send(dp); } // 释放资源 ds.close(); }catch(IOException e) { e.printStackTrace(); } } }
接收方
package cn.itcast_03; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; public class ReceiveThread implements Runnable { private DatagramSocket ds; public ReceiveThread(DatagramSocket ds) { this.ds = ds; } @Override public void run() { try { while (true) { // 创建一个数据包来接收对象 // DatagramPacket(byte[] buf, int length) byte[] bys = new byte[1024]; // int length = bys.length; DatagramPacket dp = new DatagramPacket(bys, bys.length); // 调用Socket对象的接收方法来接收数据 // public void receive(DatagramPacket p) ds.receive(dp); // 解析数据包,显示在控制台 // 获取对方的ip // InetAddress address = dp.getAddress(); // String ip = address.getHostAddress(); String ip = dp.getAddress().getHostAddress(); // public byte[] getData():获取数据缓冲区 // byte[] bys2 = dp.getData(); // public int getLength():获取数据的实际长度 // int len = dp.getLength(); String s = new String(dp.getData(), 0, dp.getLength()); System.out.println(ip + "传递的数据是:" + s); } }catch(IOException e) { e.printStackTrace();} } }