Clients send text and image data as an undifferentiated data stream, known as a writetext stream. Because it is not differentiated into parameters, an Open Server application cannot rely on the routines it normally uses in processing incoming parameter data: srv_descfmt srv_bind, and srv_xferdata. Instead, it must use a special set of text and image routines.
An Open Server application can send text or image data back to a client in one of two ways, depending on how many columns the return row contains. If the return row contains just one column, and that column contains text or image data, it can be treated as an undifferentiated data stream, and its processing deviates from the norm. If, however, the row contains other columns in addition to a text or image column, the text or image data is processed using the describe/bind/transfer method. Note that both methods have some steps in common.
See “Processing parameter and row data” for details on the describe/bind/transfer triad of calls.
