Service Name Filter

In addition to registering service names, DdeNameService enables a server to turn its service name filter on or off. When a server turns off its service name filter, the DDEML sends the XTYP_CONNECT transaction to the server's DDE callback function whenever any client calls the DdeConnect function, regardless of the service name specified in the function. When a server turns on its service name filter, the DDEML sends the XTYP_CONNECT transaction to the server only when DdeConnect specifies a service name the server has specified in a call to DdeNameService.

By default, the service name filter is on when an application calls DdeInitialize. This default prevents the DDEML from sending the XTYP_CONNECT transaction to a server before the server has created the string handles it needs. A server can turn off its service name filter by specifying the DNS_FILTEROFF flag in a call to DdeNameService. The DNS_FILTERON flag turns on the filter.