National Instruments 320682C

Chapter 6 DDE Library

Parameter Discussion

dataFormat must be a valid data format recognized by Microsoft Windows. The following are

the valid data formats supported by Microsoft Windows:

CF_TEXT CF_PALETTE

CF_BITMAP CF_PENDATA

CF_METAFILEPICT CF_RIFF

CF_SYLK CF_WAVE

CF_DIF CF_OWNERDISPLAY

CF_TIFF CF_DSPTEXT

CF_OEMTEXT CF_DSPBITMAP

CF_DIB CF_DSPMETAFILEPICT

The Microsoft Windows 3.x Programmer's Reference contains an in-depth discussion of DDE

programming and meaning of each data format type.

Using This Function

This function allows your program, acting as a DDE server, to send data to a client that has set

up a hot or warm link.

When a hot or warm link is set up, your server callback function receives a DDE_ADVISELOOP

transaction type (xType) for a particular data object (identified by itemName). When the hot or

warm link is terminated, your server callback function receives a DDE_ADVISESTOP

transaction type for the data object.

During the period when the hot or warm link is in effect, your server program is responsible for

notifying the client whenever the value of the data object changes. When the data object's value

changes, you can call this function, AdviseDDEDataReady, or

BroadcastDDEDataReady.

AdviseDDEDataReady differs from BroadcastDDEDataReady in that you specify a

particular conversation with a client. AdviseDDEDataReady sends the data only to the

specified client, even if other clients have hot or warm links to the same item.

AdviseDDEDataReady sends the data without invoking your server callback function.

However, if there are other clients with warm links to the same item, they are all notified that

new data is available. If they request the new data, your server callback function is invoked with

the DDE_REQUESTDATA message. If you do not want to send the data to those other clients,

you must write your server callback function so that it does not call ServerDDEWrite in this

case.

If you pass NULL (0) as the dataPointer and 0 as the dataSize, no data is sent to the specified

client. Instead, all clients with warm links to the item are notified. If they request the new data,

your server callback function is invoked with the DDE_REQUESTDATA message, and you can

use the ServerDDEWrite function to send the data in response.