BroadcastSystemMessageW function (winuser.h)

Article
02/09/2023

Sends a message to the specified recipients. The recipients can be applications, installable drivers, network drivers, system-level device drivers, or any combination of these system components.

To receive additional information if the request is defined, use the BroadcastSystemMessageEx function.

Syntax

long BroadcastSystemMessageW(
  [in]                DWORD   flags,
  [in, out, optional] LPDWORD lpInfo,
  [in]                UINT    Msg,
  [in]                WPARAM  wParam,
  [in]                LPARAM  lParam
);

Parameters

[in] flags

Type: DWORD

The broadcast option. This parameter can be one or more of the following values.

Value	Meaning
BSF_ALLOWSFW 0x00000080	Enables the recipient to set the foreground window while processing the message.
BSF_FLUSHDISK 0x00000004	Flushes the disk after each recipient processes the message.
BSF_FORCEIFHUNG 0x00000020	Continues to broadcast the message, even if the time-out period elapses or one of the recipients is not responding.
BSF_IGNORECURRENTTASK 0x00000002	Does not send the message to windows that belong to the current task. This prevents an application from receiving its own message.
BSF_NOHANG 0x00000008	Forces a nonresponsive application to time out. If one of the recipients times out, do not continue broadcasting the message.
BSF_NOTIMEOUTIFNOTHUNG 0x00000040	Waits for a response to the message, as long as the recipient is not being unresponsive. Does not time out.
BSF_POSTMESSAGE 0x00000010	Posts the message. Do not use in combination with BSF_QUERY.
BSF_QUERY 0x00000001	Sends the message to one recipient at a time, sending to a subsequent recipient only if the current recipient returns TRUE.
BSF_SENDNOTIFYMESSAGE 0x00000100	Sends the message using SendNotifyMessage function. Do not use in combination with BSF_QUERY.

[in, out, optional] lpInfo

Type: LPDWORD

A pointer to a variable that contains and receives information about the recipients of the message.

When the function returns, this variable receives a combination of these values identifying which recipients actually received the message.

If this parameter is NULL, the function broadcasts to all components.

This parameter can be one or more of the following values.

Value	Meaning
BSM_ALLCOMPONENTS 0x00000000	Broadcast to all system components.
BSM_ALLDESKTOPS 0x00000010	Broadcast to all desktops. Requires the SE_TCB_NAME privilege.
BSM_APPLICATIONS 0x00000008	Broadcast to applications.

[in] Msg

Type: UINT

The message to be sent.

For lists of the system-provided messages, see System-Defined Messages.

[in] wParam

Type: WPARAM

Additional message-specific information.

[in] lParam

Type: LPARAM

Additional message-specific information.

Return value

Type: long

If the function succeeds, the return value is a positive value.

If the function is unable to broadcast the message, the return value is –1.

If the dwFlags parameter is BSF_QUERY and at least one recipient returned BROADCAST_QUERY_DENY to the corresponding message, the return value is zero. To get extended error information, call GetLastError.

Remarks

If BSF_QUERY is not specified, the function sends the specified message to all requested recipients, ignoring values returned by those recipients.

The system only does marshalling for system messages (those in the range 0 to (WM_USER-1)). To send other messages (those >= WM_USER) to another process, you must do custom marshalling.

Examples

For an example, see Terminating a Process.

Note

The winuser.h header defines BroadcastSystemMessage as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll