I want to make a bandwidth display some like a digital clock that will be connected to the serial port of the computer and will show you the current bandwidth usage.
For this purpose I need the software and hardware help as I haven't done this type of experiment of programming before so please provide me some links and material that can help me I know google is the best place but I want something from you people who might have tried to do this thing before.

The things I need are a good tutorial of serial programming of linux in detail and some hardware digital display tutorial.