Problem sending command in SSH connection using Qt-creator

[Jana]

Hi,

I'm a beginner in Qt and this is my first post here.
I'm trying to set up a ssh connection to a Red Pitaya using the SshConnection integrated in the Qt Creator library. I followed this post and actually everything works except the last step. The command is not sent or not received, I don't know.
There are no error messages, but the " closed (int exitStatus) " signal of the remoteProcess is directly sent after channel is started. exitStatus is 2, but I couldn't find, what is meant by that.

My operating system is Ubuntu 14.04 and connecting via Terminal and ssh works perfectly. But I would like to start a program on the Red Pitaya directly in my Qt-Programm.

Has anyone a idea what's the problem here?
Thanks in advance!
Jana

[SGaist]

Hi and welcome to devnet,

Something's not clear: are you trying to start a remote program from your application and failing or is starting your application on the device failing from Qt Creator ?

[Jana]

Thanks for your reply. Sorry, for not describing clearly. I want to start a program on my remote device from within my Qt-application. Right now, I use Putty, connect to my device using SSH, type the command, press enter and the remote program starts. I would like to do the same from within my Qt-application.

Here's the class:

#ifndef RECEIVER_H
#define RECEIVER_H

#include <QWidget>
#include "sshconnection.h"
#include "sshremoteprocess.h"
#include "ssherrors.h"

class Receiver : public QWidget
{
    Q_OBJECT

public:
    Receiver(QWidget *parent = 0);

private slots:
    void ssh_connected();
    void onChannelStarted();
    void readyReadStandardOutput();
    void ssh_con();
    void info(int exitStatus);
    void onConnectionError(QSsh::SshError);

private:
    QSsh::SshRemoteProcess::Ptr remoteProc;
    QSsh::SshConnection *connection;
};

#endif

#include <QDebug>

#include "receiver.h"

#define CALIB_DC_OFFSET 2000

Receiver::Receiver(QWidget *parent)
    : QWidget(parent)
{
    statusLabel = new QLabel(tr("Listening for broadcasted messages"));
    statusLabel->setWordWrap(true);

    quitButton = new QPushButton(tr("&Quit"));

    connect(quitButton, SIGNAL(clicked()), this, SLOT(ssh_con()));

    QHBoxLayout *buttonLayout = new QHBoxLayout;
    buttonLayout->addStretch(1);
    buttonLayout->addWidget(quitButton);
    buttonLayout->addStretch(1);
}

void Receiver::ssh_con(){
    QSsh::SshConnectionParameters parameters;
    parameters.host =  IP;
    parameters.userName = user;
    parameters.password = password;
    parameters.timeout = 20;
    parameters.authenticationType = QSsh::SshConnectionParameters::AuthenticationTypePassword;
    parameters.port = 22;

    connection = new QSsh::SshConnection(parameters, this);
    connect( connection, SIGNAL(connected()), this, SLOT (ssh_connected()));
    connect(connection, SIGNAL(error(QSsh::SshError)), SLOT(onConnectionError(QSsh::SshError)));

    connection->connectToHost();
}

void Receiver::onConnectionError(QSsh::SshError){
    qDebug() << "Com: Connection error" << connection->errorString();
}

void Receiver::ssh_connected(){
    qDebug() << "ssh connected";
    const QByteArray command ("acquire 10 1024");  // 
    remoteProc = connection->createRemoteProcess(command);

    if(remoteProc){
        connect(remoteProc.data(), SIGNAL (started()), SLOT (onChannelStarted()));
        connect(remoteProc.data(), SIGNAL(readyReadStandardOutput()), SLOT(readyReadStandardOutput()));
        connect(remoteProc.data(), SIGNAL(closed(int)), this, SLOT(info(int)));

        remoteProc->start();
    }
}

void Receiver::info(int exitStatus){
    qDebug() << "Session closed " << exitStatus;
}

void Receiver::onChannelStarted(){
    qDebug() << "Channel started";
    qDebug() << "RemoteProc is running: " << remoteProc->isRunning();
}
void Receiver::readyReadStandardOutput(){
    qDebug() << "OUTPUT: " << remoteProc->readAll();
}

I run it, and output is:

ssh connected
Channel started
remoteProc is running: true
Session closed 2

[SGaist]

What does acquire do ?

[Jana]

"Acquire" is a program on the Red Pitaya that measures and returns voltage values. "Acquire 10 1024" should give an output of 10 rows and two columns of numbers, for example:
-163 -69
-164 -70
-163 -70
-163 -70
-162 -69
-164 -70
-165 -71
-163 -70
-163 -70
-163 -69

I also tried "ls" and "ll" as a command, but it's the same debug-output.

I don't understand why a normal ssh-connection works, but using the qt-lib doesn't...

[Jana]

I did it differently now and wrote a small script using sshpass to open the connection and send the command. In my Qt program I just start the script. It takes a bit, but it's ok ;)

[SGaist]

That's a good workaround. Are you using QProcess ?