Request Transaction

A client application can use the XTYP_REQUEST transaction to request a data item from a server application. The client calls the DdeClientTransaction function, specifying XTYP_REQUEST as the transaction type and specifying the data item the application needs.

The DDEML passes the XTYP_REQUEST transaction to the server, specifying the topic name, item name, and data format requested by the client. If the server supports the requested topic, item, and format, the server should return a data handle that identifies the current value of the item. The DDEML passes this handle to the client as the return value from DdeClientTransaction. The server should return NULL if it does not support the topic, item, or format requested.

DdeClientTransaction uses the lpdwResult parameter to return a transaction-status flag to the client. If the server does not process the XTYP_REQUEST transaction, DdeClientTransaction returns NULL, and lpdwResult points to the DDE_FNOTPROCESSED or DDE_FBUSY flag. If the DDE_FNOTPROCESSED flag is returned, the client cannot determine why the server did not process the transaction.

If a server does not support the XTYP_REQUEST transaction, it should specify the CBF_FAIL_REQUESTS filter flag in the DdeInitialize function. This flag prevents the DDEML from sending the transaction to the server.