This question is very likely to be closed because it's not on topic here.
However, there is one computer science aspect to your question, which is about the design of network file systems and NFS in particular, rather than just asking for source code. To help answer that question, here are the main papers on NFS:
They may be a challenging read, but they are worth it.
The best reference that I know of is Brent Callaghan's book NFS Illustrated. If you have access to a well-stocked university library, it should be there. Also worth mentioning is RFC 1094, which is definitely not for the faint-hearted.
Almost all good operating system design books have a section on networked file systems, and will often use NFS as a case study. Additionally, almost all Unix-like open source operating systems (e.g. Linux, BSD, OpenSolaris derivatives) come with NFS implementations.
If you can use a search engine, they are not difficult to find, but it will probably help a lot if you have the paper handy.