How to Detect "Network is Unreachable" via Ping using QProcess?

Question

I am having an issue while pinging to Destination / local IP using QProcess. QProcess returns "0" when ping is Successfull while Also when ping gives "Network is Unreachable" error (seen manually on terminal).

Actually I need to check the network connection in my application. To implement it, i used a very simple concept of ping using QProcess. I need to pop up a messagebox if there is any network error otherwise application starts normally without any popup message.

Here is my code for ping :

   bool App::pingPcuStatus(void)
   {
     const QString IP ="192.168.49.44";
     bool ret = false;
     int status;

     if ( IP == "0.0.0.0") {
        status = 1;
     }
    else {
            QProcess pingProcess;
            QString exec = "ping";
            QStringList params;
            params << "-c" << "1" << IP;
            status = pingProcess.execute(exec, params); //status = 0 , if Ping Successfull
            pingProcess.close();
     }

    ret = (status) ? false : true;
    return ret;
    }

But while debugging I found, it returns "true" even i am not conected to network. (I tried manual ping with same command on terminal, it gives "Network is Unreachable" error).

This leads to a big bug in my case.

What is the best way to capture this error using QProcess or any other way to resolve it ???

Any Idea or Suggestion are welcome.

`execute` is a static method. I don't understand why you are using an object. Ping does not return `0` when the network is unreachable... — UmNyobe, Dec 06 '12 at 08:21
@UmNyobe Thanks!!! i did'nt noticed about static method. Actually its not been along time for me to start with Qt. While I am still debugging my Code. May be it might be my mistake. As Ping should not return '0'. — skg, Dec 06 '12 at 08:31
Well if it returns `0` on success, what does it return on failure? Use that.... — Lightness Races in Orbit, Dec 06 '12 at 09:28

score 1 · Accepted Answer · edited May 23 '17 at 12:03

1

Original answer from https://stackoverflow.com/a/2148360/793796:

QProcess pingProcess;
QString exec = "ping";
QStringList params;
params << "-c" << "1" << IP;
pingProcess.start(exec,params,QIODevice::ReadOnly);
pingProcess.waitForFinished(-1);

QString p_stdout = pingProcess.readAllStandardOutput();
QString p_stderr = pingProcess.readAllStandardError();

Then you can parse stdout & stderr.

edited May 23 '17 at 12:03

Community

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answered Dec 06 '12 at 07:19

anishsane

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Thanks for your answer. Well i dont know why p_stdout and p_stderr is giving empty string everytime. – skg Dec 06 '12 at 08:35
1

For now, can you remove `-c 1` from the command line & see if the ping command is running with proper arguments? check ps for your qt process & then check its child process pid. then check `/proc/$childPid/cmdline` to verify, that the command being executed is proper. Also try adding open mode (see edit). – anishsane Dec 06 '12 at 09:36
Getting Empty String. – Shaiful Islam Jul 27 '23 at 05:47

How to Detect "Network is Unreachable" via Ping using QProcess?

1 Answers1