FindPreviousFrame function

Artikel
03/18/2022

The FindPreviousFrame function finds the previous frame in the current capture context that matches the filter.

Syntax

HFRAME WINAPI FindPreviousFrame(
   HFRAME    hCurrentFrame,
   LPSTR     ProtocolName,
   LPADDRESS DestinationAddress,
   LPADDRESS SourceAddress,
   LPWORD    ProtocolOffset,
   DWORD     OriginalFrameNumber,
   DWORD     LowestFrame
);

Parameters

hCurrentFrame

Handle to the frame.

ProtocolName

Protocol name, such as TCP.

DestinationAddress

Destination address of the frame that is searched for.

SourceAddress

Source address of the frame that is searched for.

ProtocolOffset

Pointer to a WORD that receives the protocol offset.

OriginalFrameNumber

Starting point of the search. By default, this function searches backward 1,000 frames from OriginalFrameNumber starting point. You can change the search-back distance by adding this line to the Nmapi.ini file, which is located in the \Network Monitor directory.

MAXLOOKBACK=<new lookback distance>

LowestFrame

Lowest frame number in the capture that is searched.

Return value

If the function is successful, the return value is a handle to the previous frame.

If the function is not successful, the return value is NULL.

Remarks

The capture filter is defined primarily by ProtocolName, which is the only required filter input; you can add DestinationAddress and SourceAddress information to increase the capture speed.

ProtocolOffset is returned to the calling parser, which adds this DWORD to the pointer returned by locking the frame (with ParserTemporaryLockFrame) to get the LPBYTE of the protocol that is being searched for. On return, the HFRAME that passed the filter is given to the parser. If the parser finds that the frame is not the one that is being sought, the parser can hand this HFRAME back to the FindPreviousFrame function to retrieve the next frame. The source and destination addresses, which are not required, can be passed in as NULL. When used, these addresses can be of type ADDRESS_TYPE_IP, and so on, not just MAC types.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Netmon.h
Library	Nmapi.lib
DLL	Nmapi.dll

Dela via