" So, when you create a Device::Modem::GSM object in the main thread, after the worker thread gets created, the worker thread has to use try and access the object in the main thread, crossing a safety barrier, and it is the source of all sorts of errors like you are getting. Or, if you create the Device::Modem::GSM() object before the thread is created, there are essentially 2 objects, 1 in main, and a copy in the thread... that causes boundary errors too."

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Thank you for your valuable suggestions. I am able to solve the problem.

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But as per requirements of my GUI it looks a partial solution!!!