Data Channel Problems

Hi All,
 Hope everyone is fine out there. I am developing a simple NM test
application for text chat & voice call setup.
so far I have succeeded in establi****ng the conference and making call to
remote system. After call is established I created a data channel, and
received its channel changed event and on this notification I setup the
connection point setup. after that I try to send data using Sentdata
method.
 The problem is that the data is sent, but on the destiantion i only
receives (????) symbols as data. secondly I didn't get the data sent
notification.
Can anyone tell me what could I be doing wrong ?

Regards