assignig text to text box from other class.

Question

Hi There,
i am working on a windows application, which implements communication between two systems, using TCP/IP protocol.
my form contains a multiline text box, in which i want to display the text/data received.
i am reading data on the socket using asynchronous/non-blocking method. the method for reading data on socket is in different class.
My problem is: i get data on the socket, which i pass to a function on form. but the data is not displayed in the text box. the string if displayed in message box, it is dispalyed. in short, the function on main form gets data received by server, but it is not displayed in tex box.
Please help me in the matter.
Thanks in advance.