Hi @arunraj.premraj ,
just for the sake of completeness:
it looks like that the “missing FIN” is a known topic which is a hurdle for various systems; unfortunately, in the thread below there wasn’t any fix or workaround available (it’s already some years old, I haven’t investigated further):
S7 1500: tdiscon doesn’t close the connection cleanly - Siemens SiePortal
Best regards!