TelnetClient receives no data

Question

I am trying to use the Aapche Commons Net library to implement a telnet connection in Android. I used the example to build an AsyncTask, but there seems to be no data received at all.

This is the doInBackground of my AsyncTask:

protected Long doInBackground(String... strings) {
    publishProgress("Connecting to "+target+"\n");

    try {
        Thread reader = new Thread(new Runnable() {
            @Override
            public void run() {
                InputStream in = tc.getInputStream();
                byte[] buff = new byte[1024];
                int r = 0;
                try {
                    do {
                        r = in.read(buff);
                        if (r > 0) {
                            publishProgress("[R] " + new String(buff, 0, r));
                        }
                    } while (r >= 0);
                } catch (Exception e) {
                    publishProgress(e.getClass()+": "+e.getMessage());
                } finally {
                    publishProgress("\n ++++ Disconnecting from thread.\n");
                    try {
                        tc.disconnect();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        });

        tc = new TelnetClient();
        TerminalTypeOptionHandler ttopt = new TerminalTypeOptionHandler("VT100", false, false, true, false);
        EchoOptionHandler echoopt = new EchoOptionHandler(true, false, true, false);
        SuppressGAOptionHandler gaopt = new SuppressGAOptionHandler(true, true, true, true);
        try
        {
            tc.addOptionHandler(ttopt);
            tc.addOptionHandler(echoopt);
            tc.addOptionHandler(gaopt);
        }
        catch (InvalidTelnetOptionException e)
        {
            System.err.println("Error registering option handlers: " + e.getMessage());
        }

        tc.connect(target, port);
        tc.registerNotifHandler(act);

        reader.start();

        reader.join();
    } catch (Exception e) {
        publishProgress(e.getClass()+" "+e.getMessage());
    } finally {
        publishProgress("+++ End of AsyncTask");
    }

    return 0L;
}

I think I copied all the code from the example, still I only get:

Connecting to 192.168.3.101
negcode=1, optcode=24 (this is from the notifhandler)
+++ Disconnecting from thread
+++ End of AsyncTask

When I run the example code on my laptop, it works, I do get the login from the telnet as expected.

Update It does work if I wait 1500 msecs after tc.connect(). But that's quite an ugly hack.

score 0 · Answer 1 · answered Mar 01 '16 at 19:06

0

Do not put threads in the doInBackground of an AsyncTask. Just put the code in it.

answered Mar 01 '16 at 19:06

greenapps

11,154
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Yes, I know. This was some experimenting to copy the code from the example. I had it in another part with the same results. – Bart Friederichs Mar 02 '16 at 10:02

TelnetClient receives no data

1 Answers1