Hi Peter,

A few things to try:

Get rid of the PUBLIC variable(s) and use a form property instead.
Don't wait for 5 characters before saving the .input to the form property - grab each character as it arrives, then test the string for the desired termination (CR, LF, string content, whatever).
Are you using VFP7? If so, try a INKEY(.1) prior to your DOEVENTS call to give it something to do. And play with the value.
I also see no reason in your code to continually open and close the port, at least between sends. You may have your reasons :-)
Last but not least, don't attempt any real debugging of this with the Debugger open. It may well be affecting your results. Timing things, you know...