TCP/IP Application Layer Protocols’ Execution

Does anyone know where TCP/IP Application Layer Protocols execute/initate their functionality?
Is it at the OS’s DLLs, Kernel, or Assembler?

(I imagine they don’t operate below a specific domain of computer architecture abstraction, so these options were posted).

Also, is there any way someone can view that data like a TCP/IP data packet?
Or are these protocols actually machine code?

I’ve done research but the answer came to no avail…

Someone, please respond to any one of these questions(I’m dying to know).
Thanks!