Implement some basic exception handling so that the GUI knows, when somethings wrong with the communication.

At the moment, every error printed to the user is hard-coded to be used as a terminal application. This is quick'n'dirty, yet functional. but sometimes in the future there will be a graphical user interface. then this is the place to be for every error. But on the other hand, to have some GUI elements in the communications oder data formatting parts of the project, is not favorable. Therefore every part of the program should return some kind of error indicator, and then the GUI knows what it means and produces some graphical output for recognition by the user.