UDP向host:port发送请求并返回响应。

import java.io.IOException;

import java.net.DatagramPacket;/*nowjava - 时  代  Java*/

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.net.SocketTimeoutException;


public class Main{

    public static void main(String[] argv) throws Exception{

        String host = "nowjava.com";

        int port = 2;

        String request = "nowjava.com";

        System.out.println(getResponse(host,port,request));

    }

    private static final String CLASS_NAME = UDPClientUtil.class

            .getSimpleName();

    private static final int TIMEOUT = 10 * 1000;

    /**

     * Sends a request to the host:port and returns the response.

     *   

     * @param host

     * @param port

     * @param request

     * @throws IOException

     */

    public static String getResponse(String host, int port, String request)

            throws IOException {

        String method = CLASS_NAME + ".getResponse()";/**from 时 代 J a v a - N o w J a v a . c o m**/

        DatagramSocket socket = new DatagramSocket();

        socket.setSoTimeout(TIMEOUT);


        InetAddress addr = InetAddress.getByName(host);


        byte[] data = request.getBytes();

        DatagramPacket packet = new DatagramPacket(data, 0, data.length,

                addr, port);

        LogUtil.log(method, "Sending request: " + request);

        socket.send(packet);

        LogUtil.log(method, "DONE Sending request: " + request);


        byte[] buf = new byte[1024];

        DatagramPacket datagramPacket = new DatagramPacket(buf, 0,

                buf.length, packet.getAddress(), packet.getPort());

        LogUtil.log(method, "Waiting for response.");

        try {

            socket.receive(datagramPacket);

        } catch (SocketTimeoutException ex) {

            LogUtil.log(method,

                    "Read timed out. No response received after " + TIMEOUT

                            + "ms. Returning null.");

            return null;

        }


        String response = new String(datagramPacket.getData(), 0,

                datagramPacket.getLength());

        LogUtil.log(method, "Got response: " + response);

        socket.close();

        return response;

    }

    /**

     * Send article data gram packet to given host.

     *   

     * @param host

     * @param port

     * @param article

     * @throws IOException

     */