Java Learning Note 52 (Network programming: UDP protocol Case)

InetAddress class:

Represents an IP address in the Internet, example:

 Packagedemo;Importjava.net.InetAddress;Importjava.net.UnknownHostException; Public classInetaddressdemo { Public Static voidMain (string[] args)throwsunknownhostexception {function1 ();    Function2 (); }     Public Static voidFunction1 ()throwsunknownhostexception {inetaddress inet=Inetaddress.getlocalhost (); System.out.println (Inet.gethostname ());//Get host name//Output: Desktop-q3o8aeoSystem.out.println (Inet.gethostaddress ());//Get host IP//Output: 192.168.87.1    }     Public Static voidFunction2 ()throwsunknownhostexception {//Get additional IPInetAddress inet = Inetaddress.getbyname ("www.baidu.com");        System.out.println (inet); //Output: www.baidu.com/111.13.100.92    }}

View Code

UDP protocol: No connection communication protocol, maximum 64KB, unsafe

TCP protocol: Connection-oriented communication protocol, reliable and secure, three-time handshake to confirm the connection, relatively slow, suitable for large data transmission

UDP Example:

Send side:

 Packagedemo;Importjava.io.IOException;ImportJava.net.DatagramPacket;ImportJava.net.DatagramSocket;Importjava.net.InetAddress; Public classUdpsend { Public Static voidMain (string[] args) {Try {            byte[] data = "Hello". GetBytes (); InetAddress inet= Inetaddress.getbyname ("127.0.0.1"); Datagrampacket DP=NewDatagrampacket (data, Data.length, inet, 6000); Datagramsocket DS=NewDatagramsocket ();            Ds.send (DP);        Ds.close (); } Catch(IOException ex) {System.out.println (ex); }    }}

View Code

Receiving end:

 Packagedemo;Importjava.io.IOException;ImportJava.net.DatagramPacket;ImportJava.net.DatagramSocket; Public classudpreceive { Public Static voidMain (string[] args) {Try{datagramsocket ds=NewDatagramsocket (6000); byte[] data =New byte[1024]; Datagrampacket DP=Newdatagrampacket (data, data.length);            Ds.receive (DP); intLength =dp.getlength (); String IP=dp.getaddress (). gethostaddress (); SYSTEM.OUT.PRINTLN (IP+ ":" +NewString (data, 0, length));        Ds.close (); } Catch(IOException ex) {System.out.println (ex); }    }}

View Code

Run the receive end first, then run the send side, the result:

Output: 127.0.0.1: Hello

Functions can be improved to achieve keyboard input chat:

Send side:

 Packagedemo;Importjava.io.IOException;ImportJava.net.DatagramPacket;ImportJava.net.DatagramSocket;Importjava.net.InetAddress;ImportJava.util.Scanner; Public classUdpsend { Public Static voidMain (string[] args) {Try{Scanner sc=NewScanner (system.in); Datagramsocket DS=NewDatagramsocket (); InetAddress inet= Inetaddress.getbyname ("127.0.0.1");  while(true) {String message=Sc.nextline (); byte[] data =message.getbytes (); Datagrampacket DP=NewDatagrampacket (data, Data.length, inet, 7000);            Ds.send (DP); }        } Catch(IOException ex) {System.out.println (ex); }    }}

View Code

Receiving end:

 Packagedemo;Importjava.io.IOException;ImportJava.net.DatagramPacket;ImportJava.net.DatagramSocket; Public classudpreceive { Public Static voidMain (string[] args) {Try{datagramsocket ds=NewDatagramsocket (7000); byte[] data =New byte[1024];  while(true) {Datagrampacket DP=Newdatagrampacket (data, data.length);                Ds.receive (DP); intLength =dp.getlength (); String IP=dp.getaddress (). gethostaddress (); SYSTEM.OUT.PRINTLN (IP+ ":" +NewString (data, 0, length)); }        } Catch(IOException ex) {System.out.println (ex); }    }}

View Code

Successively run, the message sent at the sender can be received at any time at the receiving end, here to achieve a simple chat function

You can also chat between multiple computers under the same LAN, as long as the corresponding IP address is changed

Java Learning Note 52 (Network programming: UDP protocol Case)