termsrv.dll (Terminal Server Dynamic Link Library) is the core library responsible for handling Remote Desktop connections. Within this file, specific code blocks check the licensing status and session limits. By altering specific bytes in this file, administrators can disable the check that enforces the "one user per session" rule on standard installations.
If you are using Remote Desktop Gateway or RD Web Access, patching termsrv.dll on the session host may cause licensing mismatch errors. In that case, revert the patch and deploy proper RDS CALs. termsrv.dll patch windows server 2022