Then you have to ensure that your application is run after Xorg is started. By the way, do you really need an Xorg server (outside the fact that you are using the xcb plugin) ?

I used Qextserialport from git clone https://code.google.com/p/qextserialport/ and the problem is solved to a great extent.

With Qextserialport, around 4% of the bytes get dropped at 115200 baud. On decreasing the speed to 9600, data reception is much better. Only issue is that of the initial 160-190 bytes that are received, some bytes are missing. After the initial 190 bytes, there is no loss at all. Since the loss seems to be predictable, I plan to append some known value 200 times ahead of the actual data and send the whole sequence. The known value will be neglected at the receiver end in software.

I'd rather go with building Qt using your BBB root filesystem so you can have all the most recent part you can