udptest.java

J2ME MIDP 2.0 无线设备编程的一些源码

//UDPTest.java
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

public class UDPTest extends MIDlet implements CommandListener
{
    private Command exitCommand, testCmd;//命令对象
    private Form form;
    private TextField tfSvr,tfRecv,tfSend; //通过TextField来显示信息
    private Ticker tker; //访问网络时显示滚动的标题
    public UDPTest()
    {
        form = new Form("UDP Test");
        tfSvr =new TextField("server","datagram://127.0.0.1:3000",120,TextField.URL);
        tfSend =new TextField("send","abcdefg",120,TextField.ANY);
        tfRecv =new TextField("receive","",120,TextField.ANY);
        tker = new Ticker("Testing");
        form.append(tfSvr);
        form.append(tfSend);
        form.append(tfRecv);

        exitCommand =new Command("Exit",Command.EXIT,1);
        testCmd =new Command("Send&Recv",Command.SCREEN,1);
        form.addCommand(exitCommand);
        form.addCommand(testCmd);
        form.setCommandListener(this);
    }
    protected void startApp(  ) throws MIDletStateChangeException
    {
        Display.getDisplay(this).setCurrent(form);
    }

    protected void pauseApp(  )
    {
    }

    protected void destroyApp( boolean p1 )
    {
    }

    public void commandAction(Command c,Displayable d)
    {
        if (c ==exitCommand)
        {
            destroyApp(false);
            notifyDestroyed();
        }
        else if(c ==testCmd)
        {
            form.setTicker(tker);
            new Client(form,tfRecv, tfSvr.getString(),tfSend.getString());
        }
    }
    
    private class Client extends Thread
    {
        private String connStr;
        private String strSend , strRecv;
        private Form form; //在读入数据完成后停止窗口的滚动标题
        private TextField tfRecv;
        public Client(Form f, TextField tf, String svr, String send)
        {
            form = f;
            tfRecv = tf;
            connStr = svr;
            strSend = send;
            this.start();
        }
        public void run()
        {
            try 
            {
                strRecv = sendAndRecv(connStr, strSend);
            }
            catch(Exception e)
            {System.out.println("error = "+e.getMessage());}   
            form.setTicker(null); //停止滚动标题
            tfRecv.setString(strRecv);//设置接收到的字符串
        }
    
        public String sendAndRecv (String svr, String send) throws IOException
        {//通过 SocketConnection 对象与TCP 服务器通信
            UDPDatagramConnection uc = null;
            Datagram dgSend = null; //发送数据报
            Datagram dgRecv = null; //接收数据报
            String recv=null;
            try
            {
                //创建 UDPDatagramConnection 对象
                uc = (UDPDatagramConnection)Connector.open(svr); 
                byte[] sendData = send.getBytes();
                dgSend = uc.newDatagram(sendData, sendData.length);
                dgRecv = uc.newDatagram(uc.getMaximumLength()); //按UDP包最大长度分配缓冲区
                uc.send(dgSend);
                uc.receive(dgRecv);
                if(dgRecv.getLength() >0)
                    recv = new String(dgRecv.getData(),0,sendData.length);//创建字符串
                else
                    recv = "Receive UDP Error";
            }
            catch (IOException e) 
            {
                System.out.println("UDP error = "+e.getMessage()); 
            }
            finally
            {//关闭所有对象
                if (uc != null)
                    uc.close();
                dgSend = null;
                dgRecv = null;
            }
            return recv;
        }
    }
}