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VirtualChannelWrite function pointer

Applies to: desktop apps only

Sends data from the client end of a virtual channel to a partner application on the server end.

Remote Desktop Services provides a pointer to a VirtualChannelWrite function in the CHANNEL_ENTRY_POINTS structure passed to your VirtualChannelEntry entry point.

Syntax

Copy

typedef UINT ( VCAPITYPE *VirtualChannelWrite)(
  __in  DWORD openHandle,
  __in  LPVOID pData,
  __in  ULONG dataLength,
  __in  LPVOID pUserData
);

Parameters

openHandle [in]: Handle to the virtual channel. This is the handle returned in the pOpenHandle parameter of the VirtualChannelOpen function.
pData [in]: Pointer to a buffer containing the data to write.
dataLength [in]: Specifies the number of bytes of the data in the pData buffer to write.
pUserData [in]: An application-defined value. This value is passed to your VirtualChannelOpenEvent function when the write operation is completed or canceled.

Return value

If the function succeeds, the return value is CHANNEL_RC_OK.

If an error occurs, the function returns one of the following values.

Return code	Description
CHANNEL_RC_BAD_CHANNEL_HANDLE	The pOpenHandle parameter is not valid.
CHANNEL_RC_NO_MEMORY	Indicates an out-of-memory condition.
CHANNEL_RC_NOT_CONNECTED	The client has not connected to an RD Session Host server.
CHANNEL_RC_NULL_DATA	The pData parameter is not valid.
CHANNEL_RC_ZERO_LENGTH	The dataLength parameter is zero.

Remarks

The VirtualChannelWrite function is asynchronous. When the write operation has been completed, your VirtualChannelOpenEvent function receives a CHANNEL_EVENT_WRITE_COMPLETE notification. Until that notification is received, the caller must not free or reuse the pData buffer passed to VirtualChannelWrite.

The value specified for the pUserData parameter is passed to your VirtualChannelOpenEvent function when the write operation is completed or canceled. You can use this data to identify the write operation.

The server add-in at the server end of the virtual channel calls the WTSVirtualChannelRead function to read the data written by a VirtualChannelWrite call.

Requirements