WaitNamedPipeA function (winbase.h)

Article
02/02/2023

Waits until either a time-out interval elapses or an instance of the specified named pipe is available for connection (that is, the pipe's server process has a pending ConnectNamedPipe operation on the pipe).

Syntax

BOOL WaitNamedPipeA(
  [in] LPCSTR lpNamedPipeName,
  [in] DWORD  nTimeOut
);

Parameters

[in] lpNamedPipeName

The name of the named pipe. The string must include the name of the computer on which the server process is executing. A period may be used for the servername if the pipe is local. The following pipe name format is used:

\\servername\pipe\pipename

[in] nTimeOut

The number of milliseconds that the function will wait for an instance of the named pipe to be available. You can used one of the following values instead of specifying a number of milliseconds.

Value	Meaning
NMPWAIT_USE_DEFAULT_WAIT 0x00000000	The time-out interval is the default value specified by the server process in the CreateNamedPipe function.
NMPWAIT_WAIT_FOREVER 0xffffffff	The function does not return until an instance of the named pipe is available.

Return value

If an instance of the pipe is available before the time-out interval elapses, the return value is nonzero.

If an instance of the pipe is not available before the time-out interval elapses, the return value is zero. To get extended error information, call GetLastError.

Remarks

If no instances of the specified named pipe exist, the WaitNamedPipe function returns immediately, regardless of the time-out value.

If the time-out interval expires, the WaitNamedPipe function will fail with the error ERROR_SEM_TIMEOUT.

If the function succeeds, the process should use the CreateFile function to open a handle to the named pipe. A return value of TRUE indicates that there is at least one instance of the pipe available. A subsequent CreateFile call to the pipe can fail, because the instance was closed by the server or opened by another client.

Windows 10, version 1709: Pipes are only supported within an app-container; ie, from one UWP process to another UWP process that's part of the same app. Also, named pipes must use the syntax \\.\pipe\LOCAL\ for the pipe name.

Examples

For an example, see Named Pipe Client.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps \| UWP apps]
Minimum supported server	Windows 2000 Server [desktop apps \| UWP apps]
Target Platform	Windows
Header	winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll

Share via