RasDialFunc callback function

The RasDialFunc callback function is called by the RasDial function when a change of state occurs during a RAS connection process.


void CALLBACK RasDialFunc(
  _In_ UINT         unMsg,
  _In_ RASCONNSTATE rasconnstate,
  _In_ DWORD        dwError


unMsg [in]

Specifies the type of event that has occurred. Currently, the only event defined is WM_RASDIALEVENT.

rasconnstate [in]

Specifies the RASCONNSTATE enumerator value that indicates the state the RasDial remote access connection process is about to enter.

dwError [in]

Specifies the error that has occurred, or zero if no error has occurred.

RasDial calls RasDialFunc with dwError set to zero upon entry to each connection state. If an error occurs within a state, RasDialFunc is called again with a nonzero dwError value.

Return value

This callback function does not return a value.


A RasDial connection operation is suspended during a call to a RasDialFunc callback function. For that reason, the RasDialFunc implementation should generally return as quickly as possible. There are two exceptions to that rule. Asynchronous (slow) devices such as modems often have time-out periods measured in seconds rather than milliseconds; a slow return from a RasDialFunc function is generally not a problem. The prompt return requirement also does not apply when dwError is nonzero, indicating that an error has occurred. It is safe, for example, to put up an error dialog box and wait for user input.

The RasDialFunc implementation should not depend on the order or occurrence of particular RASCONNSTATE connection states, because this may vary between platforms.

Do not call the RasDial function from within a RasDialFunc callback function. Call the RasGetConnectStatus, RasEnumEntries, RasEnumConnections, RasGetErrorString, and RasHangUp functions from within the callback function. For example, calling RasGetConnectStatus from within a callback function would be useful to determine the name and type of the connecting device.

Note  For convenience, RasHangUp can be called from within a RasDialFunc callback function. However, much of the hang-up processing occurs after the RasDialFunc callback function has returned.
Note  RasDialFunc is a placeholder for the application-defined or library-defined function name.


Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]



See also

Remote Access Service (RAS) Overview
Remote Access Service Functions



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