UDP Programming of Java Network program

1.UDP Introduction

Send a message using UDP, the other party does not necessarily receive, because all the information is sent in the form of a datagram, which requires the client to always wait for the message sent by the receiving server, Use the Datagramsocket class and the Datagrampacket class in Java to complete the development of a UDP program.

2. Program implementation

Use the Datagrampacket class to wrap a message that you want to send, and then use the Datagramsocket class to complete the send operation of the information. Common methods of the Datagrampacket class:

Type	Method	Describe
Structure	DatagramPacket(byte[] buf, int length)	Constructed to DatagramPacket receive packets of length length .
Structure	DatagramPacket(byte[] buf, int length, InetAddress address, int port)	Constructs a datagram package that is used to length send a package of length to a specified port number on a specified host.
Byte[]	getData()	Returns the data buffer.
int	getLength()	Returns the length of the data that will be sent or received.

Common methods of the Datagramsocket class:

Type	Method	Describe
Structure	DatagramSocket(int port)	Creates a datagram socket and binds it to the specified port on the local host.
void	send(DatagramPacket p)	Sends a datagram packet from this socket.
void	receive(DatagramPacket p)	Receives a datagram packet from this socket.

Server-side:

 Packageorg.demo.net;ImportJava.net.DatagramPacket;ImportJava.net.DatagramSocket;Importjava.net.InetAddress; Public classUdpserver { Public Static voidMain (string[] args)throwsexception{datagramsocket DS=NULL; Datagrampacket DP=NULL; DS=NewDatagramsocket (3000); String Str= "Hello"; DP=NewDatagrampacket (Str.getbytes (), Str.length (), Inetaddress.getbyname ("localhost"), 9000); System.out.println ("Send a message. ");        Ds.send (DP);    Ds.close (); }}

Operation Result:

Client:

 Packageorg.demo.net;ImportJava.net.DatagramPacket;ImportJava.net.DatagramSocket; Public classUdpClient { Public Static voidMain (string[] args)throwsexception{datagramsocket DS=NULL; byte[] buf =New byte[1024];//defines a byte array to receive dataDatagrampacket DP =NULL; DS=NewDatagramsocket (9000); DP=NewDatagrampacket (buf,1024); System.out.println ("Wait for data to be received. ");        Ds.receive (DP); String Str=NewString (Dp.getdata (), 0,dp.getlength ()) + "from" +dp.getaddress (). Gethostaddress () + ":" +Dp.getport ();        System.out.println (str);    Ds.close (); }}

Operation Result:

UDP Programming of Java Network program