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From dirk.kas...@pansoft.de
Subject [net] commons net TelnetClient inputstream blocks too long
Date Tue, 23 Sep 2008 20:48:14 GMT
Hi,
I've got an telnet enabled device of wich I could read the actual
temperature and humidness. If I connect to this device via telnet
everything works as it should. Following you could see an example telnet
session:

output of telnet connection:
$ telnet
telnet> toggle prettydump
Will print user readable output for "netdata".
telnet> open 192.168.127.254 4002
Trying 192.168.127.254...
Connected to 192.168.127.254.
Escape character is '^]'.
{x00A}
{ $x00AJB
{x00V}
{ $x00V1.0\
{x00D}
{ $x00DT071077F123032201I
{x00M}
{ $x00MT027.3F032.5P

So I wrote a little Test Application doing the (as I think) same via the
commons net API. Output of my Application is as follows:

Consoleoutput of java program:
server alive:true
Requesting {x00A}
Response:    {
Requesting {x00V}
Response:     $x00AJB
Requesting {x00D}
Response:    { $x00V1.0\
Requesting {x00M}
Response:    { $x00DT067077F168032242\

After the first command I got an incomplete response. After sending the
second command I get the remaining of what should be the first response,
after the third command I get the response of my second request and so
on... Finally I don't get the last response at all, as long as I try to
read.

Here is the source of my java Application:

package de.test;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.SocketException;

import org.apache.commons.net.telnet.TelnetClient;


public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        TelnetClient tc = new TelnetClient();

        try {
            tc.connect("192.168.127.254", 4002);
        } catch (SocketException e) {
            e.printStackTrace();
            System.exit(1);
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }

        InputStream instream = tc.getInputStream();
        OutputStream outstream = tc.getOutputStream();

        try {
            try {
                boolean alive = tc.sendAYT(10000);
                System.out.println("server alive:" + alive);
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            // be sure no data awaits reading before sending first command
            readResponse(instream);

            outstream.write("{x00A}\r\n".getBytes());
            outstream.flush();
            System.out.println("Requesting {x00A}");

            String response = readResponse(instream);
            System.out.println("Response:\t" + response);

            System.out.println("Requesting {x00V}");
            outstream.write("{x00V}\r\n".getBytes());
            outstream.flush();

            response = readResponse(instream);
            System.out.println("Response:\t" + response);

            System.out.println("Requesting {x00D}");
            outstream.write("{x00D}\r\n".getBytes());
            outstream.flush();

            response = readResponse(instream);
            System.out.println("Response:\t" + response);

            System.out.println("Requesting {x00M}");
            outstream.write("{x00M}\r\n".getBytes());
            outstream.flush();

            response = readResponse(instream);
            System.out.println("Response:\t" + response);
        } catch (IOException e) {
            e.printStackTrace();
        } finally
        {
            try {
                tc.disconnect();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static String readResponse(InputStream instream) throws
IOException {
        StringBuilder result = new StringBuilder();

        while (instream.available() == 0)
        {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        byte[] buffer = new byte[1024];
        while (instream.available() > 0)
        {
            int count = instream.read(buffer);
            result.append(new String(buffer, 0, count));
        }
        return result.toString();
    }
}



Am I doing something wrong or is there an Bug in the stream
implementation of the TelnetClient's inputStream?
By the way, if I run the TelnetClientExample of the commons net package,
the effect is the same as with my java program. After typing the first
command the response is only an '{'. After the second command the
remaining of the response gets written to System.out and so on.

thanks for your Help in advance,
Dirk Kaspar



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