next topic »

[on:]

Hi I have a problem with a tcp socket.
I can send a string command to arduino ethernet shield. All is OK.
But I can't read Arduino reply (it should be "200 OK").
Always there is an exception

This is the java code used to talk to Arduino

Code:

try {
            outStream.writeBytes(message);
            outStream.flush();
            outStream.close();
      } catch (Exception ex) {
            System.err.println("Unable to write " + message + " " + socket.toString()
                    + ". Maybe the device is not connected.");
        }
      try {
            inStream = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            System.out.print("Received string: '");

            while (!inStream.ready()) {}
            System.out.println(inStream.readLine()); // Read one line and output it

            System.out.print("'\n");
            inStream.close();
          } catch(Exception e) {
                     System.out.print("It didn't work!\n");
               }
      socket.close();

     }

The problem is with inStream section

Thanks

[Reply #1 on:]

But I can't read Arduino reply (it should be "200 OK").

Have you confirmed that the Arduino puts that string into the socket? e.g. by printing it to Serial.println(s) too?

When reading from a socket you never know if data comes in one pieces or in many pieces. Especially from a relative slow device as an Arduino it can be split in pieces.

Always there is an exception

Can you tell us what the exception tells you?

change   System.out.print("It didn't work!\n");  ==> System.out.print(e.getMessage());

[Reply #2 on:]

Thanks,I'll try to print exception message.
But if I connect to Arduino by web browser I receive the correct string. All works!!

[Reply #3 on:]

But if I connect to Arduino by web browser I receive the correct string. All works!!

That implies that your webbrowser waits until all data is received, while your program doesn't.

[Reply #4 on:]

I receive this exception

java.net.SocketException: socket is fclose

But I close the socket after reading Arduino reply.
Can you help me?

[Reply #5 on:]

The smippet of code you posted obviously doesn't tell the whole story. You need to post more of your code.

[Reply #6 on:]

This is the complete code for my function sending a message to arduino ethernet shield. It is part of a domotic project more complex

Code:

public class ETHArduinoBoard extends Actuator {

    Properties protocol = new Properties(); //defines the protocol using a hashmap
    Socket socket = null;
    DataOutputStream outStream = null;
    BufferedReader inStream = null;
    String response = null;

    public ETHArduinoBoard() {
        super("ETH Arduino Board");
        //fillProtocolData();
        //connect(); //connects to eth device
        start(); //starts the plugin
    }


  private void connect(Command c) {
      try {
            socket = new Socket(c.getProperty("socket-host"), new Integer(c.getProperty("socket-port")));
            BufferedOutputStream buffOut = new BufferedOutputStream (socket.getOutputStream ());
            outStream = new DataOutputStream (buffOut);
          } catch (UnknownHostException e) {
            System.err.println("Unable to connect to host '" + configuration.getProperty("socket-host") + "' on port " + configuration.getProperty("socket-port"));
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for "
                    + "the connection to " + c.getProperty("socket-host") + "' on port " + c.getProperty("socket-port"));

        }
//        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
    }


    @Override
   public void onCommand(Command c) throws IOException, UnableToExecuteException {
      ElectricDevice dev = getDevice(c);
      connect(c); // called here to interact with arduino
      String message = createMessage(c);
      try {
            outStream.writeBytes(message);
            outStream.flush();
            outStream.close();
            //in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            //String response = in.readLine();
            //System.out.println("Device answer:"+response+"\n");
            //in.close();
            //socket.close();
          } catch (Exception ex) {
            System.err.println("Unable to write " + message + " " + socket.toString()
                    + ". Maybe the device is not connected.");
        }
      try {
            inStream = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            System.out.print("Received string: '");

            while (!inStream.ready()) {}
            System.out.println(inStream.readLine()); // Read one line and output it

            System.out.print("'\n");
            inStream.close();
          } catch(Exception e) {
                     //System.out.print("It didn't work!\n");
                     System.out.print(e);
               }
      socket.close();

     }

   // create message to send to Arduino
   public String createMessage(Command c) {
     String message=null;
        message="GET /" + c.getProperty("code") + " HTTP 1.0\r\n\r\n";
        return(message);
       }

    private ElectricDevice getDevice(Command c) {
        //getting a safe reference to the targer object if exist
        ElectricDevice dev = null;
        try {
            dev = c.getTargetObject(ElectricDevice.class);
        } catch (NoObjectFoundException ex) {
            System.err.println("Undefined target object '" + c.getProperty("object") + "' in command '" + c.getName() + "'");
        } catch (ClassCastException classEx) {
            System.err.println("Attempt to handle an '" + c.getProperty("object") + "' as an 'ElectricDevice' -> " + classEx.getLocalizedMessage());
        }
        return dev;
    }


    /*
     * used only to update the state of the object in Freedom
     */
    protected void setTargetObjectBehavior(Command c) {
        ElectricDevice dev = getDevice(c);

        //getting the behavior to apply
        String state = c.getBehavior();

        try {
            if (state.equalsIgnoreCase("on")) {
                dev.switchOn(c.getProperties());
            }
            if (state.equalsIgnoreCase("off")) {
                dev.switchOff(c.getProperties());
            }
            if (state.equalsIgnoreCase("dim")) {
                Light light = (Light) dev;
                light.dim(c.getProperties());
            }
        } catch (Exception e) {
            System.err.println("Unable to change behavior");
        }
    }

    public void onDataAvailable(String data) {
        //do nothing
    }

    public boolean canExecute(Command c) {
        throw new UnsupportedOperationException("Not supported yet.");
    }
}

[Reply #7 on:]

What triggers the onCommand() callback?

What happens if you don't close outStream until just before you close the socket?

[Reply #8 on:]

Thanks PaulS!! You're a genius!!

I solved moving outStream.close() after reading from inStream:

 inStream.close();
 outStream.close();
 socket.close();