This tool is used for reverse-engineering of Steam client. It's capable of hooking and recording network traffic sent/received by the client. If you're not trying to implement missing SK2 functionality in ASF, then please do not proceed.

Launch Steam client
Execute hook.bat
Reproduce the functionality you're trying to add
Execute unhook.bat
Use NetHookAnalyzer2.exe for analyzing recorded log (which can be found in your Steam directory)

Source of the NetHook2.dll can be found here
Source of the NetHookAnalyzer2.exe can be found here

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There is absolutely no guarantee that this will even work for you, not to mention the consequences from hooking the external DLL into steam client. You're on your own.