threadedechohandler.java

Bluetooth echo between pc server and client

// ThreadedEchoHandler.java
// Andrew Davison, [e-mail], August 2005

/* A threaded handler, called by EchoServer to deal with a client.

   When a message comes in, it is sent back converted to uppercase.

   The handler also communicates with the top-level MIDlet (ecm)
   to add and decrement itself from the count of handlers, and
   to display a received message.

   closeDown() terminates the handler.

   ThreadedEchoHandler uses the same readData() and sendMessage()
   methods as EchoClient.
*/

import java.io.*;
import javax.microedition.io.*;
import javax.bluetooth.*;


public class ThreadedEchoHandler extends Thread
{
  private EchoServerMIDlet ecm;  // top-level MIDlet

  private StreamConnection conn; // client connection
  private InputStream in;
  private OutputStream out;

  private boolean isRunning = false;
  private String clientName;


  public ThreadedEchoHandler(StreamConnection conn, EchoServerMIDlet ecm)
  {
    this.conn = conn;
    this.ecm = ecm;

    System.out.println("Client Handler spawned");
    // store the name of the connected client
    try {
      RemoteDevice rd = RemoteDevice.getRemoteDevice(conn);
      clientName = getDeviceName(rd);
      System.out.println("Client name: " + clientName);
    }
    catch(Exception e) {}
  } // end of ThreadedEchoHandler()


  private String getDeviceName(RemoteDevice dev)
  /* Return the 'friendly' name of the device being examined,
     or "Device ??" */
  {
    String devName;
    try {
      devName = dev.getFriendlyName(false);  // to reduce connections
    }
    catch (IOException e) 
    { devName = "Device ??";  }
    return devName;
  }  // end of getDeviceName()


  public void run()
  /* Get an InputStream and OutputStream from the stream connection,
     and start processing client messages. */
  {
    ecm.incrCount();   // tell top-level MIDlet there's a new handler
    try {
      // Get I/O streams from the stream connection
      in = conn.openInputStream();
      out = conn.openOutputStream();

      processClient();
    }
    catch(Exception e)
    {  System.out.println(e);  }

    ecm.decrCount();  // remove this handler from the top-level count
  }  // end of run()


   private void processClient()
   /* When a client message comes in, echo it back in uppercase.
      If the client sends "bye$$", or there's a problem, then
      terminate processing, and the handler.
   */
   {
     isRunning = true;
     String line;
     while (isRunning) {
       if((line = readData()) == null)
         isRunning = false;
       else {  // there was some input
         System.out.println(clientName + " sent: " + line);
         if (line.trim().equals("bye$$"))
           isRunning = false;
         else {
           ecm.showMessage(clientName + ": " + line);  // show at top-level
           String upper = line.trim().toUpperCase();
           if (isRunning)
             sendMessage(upper);
         }
       }
     }
     System.out.println("Handler finished");
   }  // end of processClient()


  public void closeDown()
  // close down the handler
  {
    System.out.println("Close down echo handler");
    isRunning = false;
    try {
      if (conn != null) {
        in.close();
        out.close();
        conn.close();
      }
    }
    catch (IOException e) 
    {  System.out.println(e);  }
  }  // end of closeDown()


  // --------------- IO methods ---------------------------
  // Same as the methods in EchoClient


  private String readData()
  /* Read a message in the form "<length> msg".
     The length allows us to know exactly how many bytes to read
     to get the complete message. Only the message part (msg) is
     returned, or null if there's been a problem.
  */
  { byte[] data = null;   
    try {       	      	
      int len = in.read();    // get the message length
      if (len <= 0) {
        System.out.println("Message Length Error");
        return null;
      }
   
      data = new byte[len];
      len = 0;
      // read the message, perhaps requiring several read() calls 
      while (len != data.length) {     
        int ch = in.read(data, len, data.length - len);
        if (ch == -1) {
          System.out.println("Message Read Error");
          return null;
        }
        len += ch;
      }      
    } 
    catch (IOException e) 
    {  System.out.println("readData(): " + e); 
       return null;
    } 

    // System.out.println("readData: " + new String(data));
    return new String(data);  // convert byte[] to String
  }   // end of readData()


  private boolean sendMessage(String msg)
  // the message format is "<length> msg" in byte form
  {
    System.out.println("sendMessage: " + msg);
    try {
      out.write(msg.length());
      out.write(msg.getBytes());
      return true;
    } 
    catch (Exception e) 
    {  System.out.println("sendMessage(): " + e);  
       return false;
    } 
  }  // end of sendMessage()

}  // end of ThreadedEchoHandler class