9P - Plan 9 File Protocol

9P is a network protocol developed at Bell Labs for the Plan 9 from Bell Labs distributed operating system as the means of accessing and manipulating resources and applications transparently in a distributed environment. 9P works both as a distributed file system and as a network transparent and language agnostic 'API'.

Name	Version	Client Server	Lang	OSs	License	Comments
Plan 9 from Bell Labs	9p2000	Client Server	C	Plan 9, Plan B	LPL	The original and 'reference' implementation as part of the Plan 9 operating system.
plan9port	9p2000, 9p2000.u	Client Server	C	Most Unix variants	LPL/MIT	Plan 9 from User Space(aka plan9port) is a port of many user space utilities and libraries from Plan 9 to Unix systems.
Inferno	9p2000	Client Server	Limbo	All Inferno host systems	GPL/BSD	Part of the Inferno operating system, can run hosted on top of other systems.
v9fs	9p2000, 9p2000.u	Client	C	Linux	GPL	File system driver for the Linux kernel.
py9p	9p2000	Client Server	Python	-	Public Domain	9P implementation in pure python.
libixp	9p2000	Client Server	C	All Unix variants	MIT	Originally as part of the wmii project.
Ruby-IXP	9p2000	Client Server(?)	Ruby	-	GPL	A simple and fast client implementation in pure Ruby.
Rstyx	9p2000	Client Server(?)	Ruby	-	LGPL/Ruby License	Another pure Ruby implementation.
Jstyx	9p2000	Client Server	Java	-	BSD License	A 9P implementation in pure Java, also includes special libraries for grid services.
ninep	9p2000	Client	Lisp	-	MIT	A multi-threaded client implementation in Lisp.
9pvfs.tcl	9p2000	Client Server	TCL	-	Public Domain?	Transparent access to 9P server from TCL.
9pc	9p2000	Client Server	C#	-	Public Domain?	9P for .NET environments.
rii	9p2000	Client	C/Ruby	-	MIT?	Ruby bindings to the libixp library.
ocaml-9p	9p2000	Client	Ocaml	-	BSD	OCaml-9P is a pure OCaml implementation.
styx-n-9p	9p2000	Client	Java	-	MIT	Client only multi-threaded Java implementation including Inferno authentication support.
r9p	9p2000	Client	Ruby	-	MIT	A simple client implementation for Ruby. It supports the operations of the IO class by providing a true file descriptor through a proxy thread.
9puffs	9p2000	Client	C	NetBSD	BSD	Userspace file system driver implemented on top of puffs.

• What is 9P2000? 9P2000 is the latest version of the 9P protocol which was introduced with Plan 9 from Bell Labs 4th Edition; it introduced certain simplifications of the protocol. Previous versions of the protocol are deprecated and are rarely used anymore.
• What is the difference between Styx and 9P? In all recent versions of Inferno Styx is the same as 9P2000. Styx was a variant of the original 9P protocol for Inferno, most of those changes were rolled into 9P2000 and Inferno itself switched to use the new version of the protocol but keep the same name. This days some people use the name 'Styx' to mean 9P2000 using Inferno authentication by default.
• What is 9P2000.u(aka .u)? It is a set of extensions to 9P2000 as part of the v9fs project to support aspects of legacy Unix file systems that 9P never included because Plan 9 didn't need them(eg., SUID bit).