termsrv.dll is a critical system library located in C:\Windows\System32 . It is responsible for managing Terminal Services (now called Remote Desktop Services) on Windows Server. This DLL governs:

You're looking for information on a universal termsrv.dll patch for Windows Server 2012 R2.

net stop TermService /y

After patching, the server no longer checks or enforces the concurrent user limit. Any number of administrators (or users) can connect simultaneously via RDP using the same administrative credentials or different local accounts.

Using a disassembler (IDA Pro, Ghidra, or x64dbg) on %SystemRoot%\System32\termsrv.dll (x64 version for Server 2012 R2), the relevant code appears as: