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One of the three elements IP address
In class A:
(1) 10.XXX is a private address (a private address is not used on the Internet)
(2) 127.XXX is a reserved address
Category A China has only three government telecommunications military departments, most of which are in the United States
In class B:
(1) 172.16.0.0 --- 172.31.255.255 is a private address
(2) 169.254.XX is a reserved address
Class B is generally the campus network of the university
In class C:
192.168.XX is a private address
We generally use class C
======================
Two related DOS commands:
ipconfig to view the local ip address
Ping is followed by the ip address to test whether there is a problem with the communication between the machine and the specified ip address
Special IP address:
127.0.0.1 loopback address (representing this machine)
XXX255 broadcast address
XXX0 network address
The second of the three elements Port number
The third of the three elements Agreement
rules of communication
three-way handshake protocol TCP
A: Send request B: Reply agree A: Send
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UDP protocol sending protocol
A: Create the sender's Socket object
B: Create data and package data
C: Call the Socket object send method to send data
D: release resources
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();
//create packet
// send data packet
//public void send(DatagramPacket p);
byte[] bys = "hello, udp, here I come.".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);
// release resources
ds.close();
}
}
UDP protocol receiving protocol
A: Create the sender's Socket object
B: Create a packet (accept container)
C: Call the Socket object receive method to receive data
D: Parse the packet and display it in the console
E: release resources
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 {
//Create Socket object
//Construct DatagramSocket(int port) with parameters
DatagramSocket ds = new DatagramSocket(10086);
//Create a packet to receive the object
//DatagramPacket(byte[] buf, int length)
byte[] bys = new byte[1024];
int length = bys.length;
DatagramPacket dp = new DatagramPacket(bys,length);
//Call the receive method of the Socket object to receive data
// public void receive(DatagramPacket p)
ds.receive(dp);
// Parse the packet and display it in the console
//Get the other party's ip
InetAddress address = dp.getAddress();
String ip = address.getHostAddress();
//public byte[] getData(): Get the data buffer
byte[] bys2 = dp.getData();
//public int getLength(): Get the actual length of the data
int len = dp.getLength();
String s = new String(bys2,0,len);
System.out.println(ip+"The data passed is: "+s);
// release resources
ds.close();
}
}
====================
diagram
=====================
Main program:
package cn.itcast_03;
import java.io.IOException;
import java.net.DatagramSocket;
import java.net.SocketException;
/*
* Improve the method of changing talents through multi-threading, so that you can send and receive data in one window
*
*
*/
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();
}
}
sender:
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 {
// Encapsulate keyboard input data
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String line = null;
while ((line = br.readLine()) != null) {
byte[] bys = line.getBytes();
// create packet
// send packet
// public void send(DatagramPacket p);
// byte[] bys = "hello,udp, here I come.".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);
}
// release resources
ds.close();
}catch(IOException e) {
e.printStackTrace ();
}
}
}
receiver
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) {
// create a packet to receive the object
// DatagramPacket(byte[] buf, int length)
byte[] bys = new byte[1024];
// int length = bys.length;
DatagramPacket dp = new DatagramPacket(bys, bys.length);
// Call the receive method of the Socket object to receive data
// public void receive(DatagramPacket p)
ds.receive(dp);
// Parse the packet and display it in the console
// get the other party's ip
// InetAddress address = dp.getAddress();
// String ip = address.getHostAddress();
String ip = dp.getAddress().getHostAddress();
// public byte[] getData(): Get the data buffer
// byte[] bys2 = dp.getData();
// public int getLength(): Get the actual length of the data
// int len = dp.getLength();
String s = new String(dp.getData(), 0, dp.getLength());
System.out.println(ip + "The data passed is: " + s);
}
}catch(IOException e) {
e.printStackTrace ();}
}
}