If you try to run the executable on a machine with no comms port in the Device Manager it will crash, I will when I have chance correct this!, to get around this please ensure a Communication Port available in Device Manager.
RS-232 is the best know method of PC Communications, the characteristics of RS232 is a logic 1 (true) is can range from -3v to -25v a logic 0 (false) +3v to +25v. The area of -3v to 0 to +3v is taken as not valid to allow for noise and interference on the line. If the port is idle the port is at high level (or -12v), which is why if you look at circuit diagrams of peripherals there is always to a lot of invertors. RS-485 detailed at the end, RS-422 & RS-449 and on to allow very long cable runs and high speeds all follow the same basic path.