Advice on communicating with the serial port

Hi people,

I am supposed to communicate with a cashcard reader through the COM port but i have no previous experience interfacing with it.

I do not have one in my office but i am able to borrow it for two days for testing.

To maximize the two days, i hope to be more prepared. i have read up on some basic vb codes on communicating with it already.
But i do not know how can i verify whether my codes work anot..

e.g whether it received the string it should receive
Can you guys give some advice?

- I heard some people saying a DLL file of the reader, if i do get it.. how am i going to know what functions are inside the Dll file.

-if i do not get it , how am i going to communicate with the reader.. e.g. i send some strings over and can verify that it has received it correctly.
very basic testing..

- what else should i look out for / other helpful advice


I need to test some basic two-way communication with it.

thanks