B4J Question B4J libraries for hardware under Linux

[peacemaker]

Hi, All

According the info i have found - under Linux the COM-ports, Bluetooth and stereo-audio output do not work with B4J libraries that are well known under Windows.

Maybe anyone touched it under Linux ?
What libs are needed for B4J under Linux ?

 

[aeric]

I only use COM ports in Linux with jSerial.
Search the forum. You need to add a special user group if you want to avoid using sudo.

 

[peacemaker]

I only use COM ports in Linux with jSerial.

So, code is the same as for Windows ? Do you mean the port cannot be open due to some permission ?

 

[aeric]

So, code is the same as for Windows ? Do you mean the port cannot be open due to some permission ?

Yes, the code is same for async stream.
The difference is the name of the com port.
You need permission to work with the COM port in Linux.

Serial in Linux

Hello All, I am trying to use the JSerial lib in ubuntu with no success. Anyone knows if I can use this Lib in Linux ? I get an exception error when i try to open the com1 (its working and reported in system) /dev/ttyS0 And even a simple application to list all ports serial.listports returns a...

www.b4x.com

 

[peacemaker]

Thanks, Aeric, indeed.
I have set up WSL2 like here https://learn.microsoft.com/en-us/windows/wsl/connect-usb, and it can detect the serial device, but only under SUDO.

    #if B4J
        #if LinuxDebugging or LinuxProduction
            Dim USBportPrefix As String = "/dev/tty"    '/dev/ttyUSB0
        #else
            Dim USBportPrefix As String = "COM" 'Windows COM-ports
        #End If
    #Else if B4A
        Dim USBportPrefix As String = "/dev/bus/usb/"    '/dev/bus/usb/001/003
    #End If

But how the app should be installed\provided for end-user ? With setting up the permissions\group rights ?

 

[aeric]

Thanks, Aeric, indeed.
I have set up WSL2 like here https://learn.microsoft.com/en-us/windows/wsl/connect-usb, and it can detect the serial device, but only under SUDO.

    #if B4J
        #if LinuxDebugging or LinuxProduction
            Dim USBportPrefix As String = "/dev/tty"    '/dev/ttyUSB0
        #else
            Dim USBportPrefix As String = "COM" 'Windows COM-ports
        #End If
    #Else if B4A
        Dim USBportPrefix As String = "/dev/bus/usb/"    '/dev/bus/usb/001/003
    #End If

But how the app should be installed\provided for end-user ? With setting up the permissions\group rights ?

I only can think that the step for setting permission is outside the installer.

 

[peacemaker]

And if to detach the serial device from USB port - fatal crashing under Linux:

/dev/ttyUSB0: data is ОК
terminate called after throwing an instance of 'std::bad_alloc'
what(): std::bad_alloc

 

[peacemaker]

If the special permission is required for access to the COM-ports under Linux, and moreover after "sudo usermod..." the re-login is required - it means each app user must setup manually it for his user account ... brain explosion.
It is not for "windows clickers"...

 

[peacemaker]

I only use COM ports in Linux with jSerial.

Hi, @aeric

How does your Linux app process with the COM-port detaching ? If to unplug device's USB-cable.
I have internal system error that cannot be catched\wrapped and app is crashed:

terminate called after throwing an instance of 'std::bad_alloc'
what(): std::bad_alloc

 

[aeric]

Hi, @aeric

How does your Linux app process with the COM-port detaching ? If to unplug device's USB-cable.
I have internal system error that cannot be catched\wrapped and app is crashed:

I haven't tested with USB. Just serials port.

 

[peacemaker]

Just serials port.

So, if to unplug the connector during communication - where an error occured ? No crash ?

 

[aeric]

So, if to unplug the connector during communication - where an error occured ? No crash ?

Sorry, I don't do such thing.

You may want to use Try-Catch.

 

[peacemaker]

Ha !
jSerial works OK under Windows, as well known and using, but ... it works OK also under Ubuntu Linux ! Tested as part of Win10 WSL2 - virtual Linux.
But if to try on real laptop under Linux Mint21 - it does not work, port is detected, but connection is done very rare and some system error is:

terminate called after throwing an instance of 'std::bad_alloc'
what(): std::bad_alloc

Anyone seen, why different ?

 

[stevel05]

stereo-audio output do not work

It works on my old laptop, may be an audio configuration or driver issue on a device by device basis. WSL does not currently support Audio.

 

[peacemaker]

It works on my old laptop

Yes, thanks, i found other PC - the generator works there under Linux, in release mode, sure only.

Now problem is with COM-ports....

 

[stevel05]

in release mode, sure only.

As with Windows as your app uses the threading library.

 

[aminoacid]

I have been using a few B4J apps that access the serial port on both Windows and a variety of Linux Platforms (Ubuntu, Debian, etc.). Never had any issues with permissions. The default permission for the serial ports work fine. The application always runs under a sudo user. The serial ports tested are native serial ports as well as Virtual USB serial ports (/dev/ttyUSBx) using a serial/USB adapter. No issues with either.

Yes, depending on the driver, the program will crash if the USB/Serial adapter is unplugged. In some cases (driver/hardware) it will throw an exception and then automatically recover when the adapter is plugged back in. I have been unable to catch these exceptions using Try-Catch. So what I do is run the application as a systemd service and set it up so if the program crashes the service is restarted automatically. This will happen continuously until the devices is plugged in and detected again.

 

[peacemaker]

application always runs under a sudo user

Ha, this allows all.

unable to catch these exceptions using Try-Catch

Yes ! Stupid. Under Windows all works automatically and all errors catched OK.

application as a systemd service

GUI app as a service ?! How to do it ?

My app under Windows can work with many USB-COM-ports at the same time in "plug-n-play mode", any can be detected when plugged or removed in the app when unplugged OK.
But now you explained - under Linux desktop it is impossible.... unbelievable.

Even the alone USB-device cannot be unlugged without crash ?! Maybe we have to track the USB devices events some how to close the COM-port on time?

 

[aminoacid]

GUI app as a service ?! How to do it ?

No, I have never tried running a GUI app as a service. My apps are all console apps. But I don't see why a GUI app would not run? I may give it a try if I get a chance.