Java/Network Protocol/DatagramPacket
Содержание
Create DatagramPacket from byte array
<source lang="java">
import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; class Main {
public static void main(String args[]) throws Exception {
InetAddress ia = InetAddress.getByName(args[0]);
int port = Integer.parseInt(args[1]);
DatagramSocket ds = new DatagramSocket();
while (true) {
String s = "asdf";
byte buffer[] = s.getBytes();
DatagramPacket dp = new DatagramPacket(buffer, buffer.length, ia, port);
ds.send(dp);
}
}
}
</source>
Get address and port from DatagramPacket
<source lang="java">
import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; class Main {
private final static int BUFSIZE = 20;
public static void main(String args[]) throws Exception {
int port = Integer.parseInt(args[0]);
DatagramSocket ds = new DatagramSocket(port);
byte buffer[] = new byte[BUFSIZE];
while (true) {
DatagramPacket dp = new DatagramPacket(buffer, buffer.length);
ds.receive(dp);
InetAddress ia = dp.getAddress();
System.out.println(ia);
System.out.println(dp.getPort());
}
}
}
</source>
Get data from DatagramPacket
<source lang="java">
import java.net.DatagramPacket; import java.net.DatagramSocket; class DatagramReceiver {
private final static int BUFSIZE = 20;
public static void main(String args[]) throws Exception {
int port = Integer.parseInt(args[0]);
DatagramSocket ds = new DatagramSocket(port);
byte buffer[] = new byte[BUFSIZE];
while (true) {
DatagramPacket dp = new DatagramPacket(buffer, buffer.length);
ds.receive(dp);
System.out.println(new String(dp.getData()));
}
}
}
</source>
Sends the specified text or file as a datagram to the specified port of the specified host
<source lang="java">
/*
* Copyright (c) 2004 David Flanagan. All rights reserved. * This code is from the book Java Examples in a Nutshell, 3nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose, * including teaching and use in open-source projects. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book, * please visit http://www.davidflanagan.ru/javaexamples3. */
//package je3.net; import java.io.File; import java.io.FileInputStream; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; /**
* This class sends the specified text or file as a datagram to the specified * port of the specified host. */
public class UDPSend {
public static final String usage = "Usage: java UDPSend <hostname> <port> <msg>...\n"
+ " or: java UDPSend <hostname> <port> -f <file>";
public static void main(String args[]) {
try {
// Check the number of arguments
if (args.length < 3)
throw new IllegalArgumentException("Wrong number of args");
// Parse the arguments
String host = args[0];
int port = Integer.parseInt(args[1]);
// Figure out the message to send.
// If the third argument is -f, then send the contents of the file
// specified as the fourth argument. Otherwise, concatenate the
// third and all remaining arguments and send that.
byte[] message;
if (args[2].equals("-f")) {
File f = new File(args[3]);
int len = (int) f.length(); // figure out how big the file is
message = new byte[len]; // create a buffer big enough
FileInputStream in = new FileInputStream(f);
int bytes_read = 0, n;
do { // loop until we"ve read it all
n = in.read(message, bytes_read, len - bytes_read);
bytes_read += n;
} while ((bytes_read < len) && (n != -1));
} else { // Otherwise, just combine all the remaining arguments.
String msg = args[2];
for (int i = 3; i < args.length; i++)
msg += " " + args[i];
// Convert the message to bytes using UTF-8 encoding
message = msg.getBytes("UTF-8");
}
// Get the internet address of the specified host
InetAddress address = InetAddress.getByName(host);
// Initialize a datagram packet with data and address
DatagramPacket packet = new DatagramPacket(message, message.length, address, port);
// Create a datagram socket, send the packet through it, close it.
DatagramSocket dsocket = new DatagramSocket();
dsocket.send(packet);
dsocket.close();
} catch (Exception e) {
System.err.println(e);
System.err.println(usage);
}
}
}
</source>
Waits to receive datagrams sent the specified port
<source lang="java">
import java.net.DatagramPacket; import java.net.DatagramSocket; /**
* This program waits to receive datagrams sent the specified port. When it * receives one, it displays the sending host and prints the contents of the * datagram as a string. Then it loops and waits again. */
public class UDPReceive {
public static final String usage = "Usage: java UDPReceive <port>";
public static void main(String args[]) {
try {
if (args.length != 1)
throw new IllegalArgumentException("Wrong number of args");
// Get the port from the command line
int port = Integer.parseInt(args[0]);
// Create a socket to listen on the port.
DatagramSocket dsocket = new DatagramSocket(port);
// Create a buffer to read datagrams into. If anyone sends us a
// packet containing more than will fit into this buffer, the
// excess will simply be discarded!
byte[] buffer = new byte[2048];
// Create a packet to receive data into the buffer
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
// Now loop forever, waiting to receive packets and printing them.
for (;;) {
// Wait to receive a datagram
dsocket.receive(packet);
// Decode the bytes of the packet to characters, using the
// UTF-8 encoding, and then display those characters.
String msg = new String(buffer, 0, packet.getLength(), "UTF-8");
System.out.println(packet.getAddress().getHostName() + ": " + msg);
// Reset the length of the packet before reusing it.
// Prior to Java 1.1, we"d just create a new packet each time.
packet.setLength(buffer.length);
}
} catch (Exception e) {
System.err.println(e);
System.err.println(usage);
}
}
}
</source>
