help, please: serial communication on WebForms

Question

I have a web site developed under asp.net and I am in the need to comunicate with the serial port on certain clients. I am not very sure how to do this, can someone please help me. To further understand my situation here is my problem definition. I have this application that is web-based and on some clients I must send a string thru the serial port to and then listen to its response. Thanx Pedro