Two applications listening one serial port

Hello friends:
My name is Ruben and i am from Spain.
I am administrator of an online weather server.
We have a weather station connected to the serial port of the server.
Weather station ONLY sends data, doesn't receive anything from PC.
At this moment we have one software attached directly to /dev/ttyS0, but we
want test another Sotware.
What we have been testing to do this is:

tee /dev/ptyp0 /dev/ptyp1 < /dev/ttyS0 > /dev/null &

And then attach one software to /dev/ttyp0 and the other one to /dev/ttyp1

We have been testing but...some data is losen in /dev/ttypo and /dev/ttyp1
I don't understand why

Do you know if i could do this using another command?
Am i doing this Ok?

Please...we need some help, we have been some weeks fighting with it ;(

A lot of thank's.

P.D. Excuse my poor English, but i don't explain very well.

Thank's