9P (or the Plan 9 Filesystem Protocol or Styx) is a network protocol developed for the Plan 9 from Bell Labs distributed operating system as the means of connecting the components of a Plan 9 system. Files are key objects in Plan 9. They represent windows, network connections, processes, and almost anything else available in the operating system. Unlike NFS, 9P encourages caching and also serving synthetic files (e.g. /proc to represent processes).
9P was revised for the 4th edition of Plan 9 under the name 9P2000 that contained various fundamental improvements. The latest version of the Inferno operating system also uses 9P2000. The Inferno file protocol was originally called Styx, but technically it has always been a variant of 9P.
A server implementation of 9P for Unix, called u9fs, is included in the Plan 9 distribution. A kernel client driver for Linux is part of the v9fs project. 9P and its derivatives have also found application in embedded environments, such as the Styx on a Brick project.
Server applications 
Many of Plan 9's applications take the form of 9P servers. Noteworthy examples include:
- acme: a user interface for programmers
- rio: the Plan 9 windowing system.
- plumber: interprocess communication
- wikifs: a wiki
9P sends the following messages between clients and servers. These messages correspond to the entry points in the Plan 9 vfs layer that any 9P server must implement.
- Negotiate protocol version
- Return an error
- Abort a message
- auth, attach
- Messages to establish a connection
- Descend a directory hierarchy
- create, open
- Prepare a fid for I/O on an existing or new file
- read, write
- Transfer data from and to a file
- Forget about a fid
- Remove a file from a server
- stat, wstat
- Inquire or change file attributes
See also 
External links 
Wed, 15 May 2013 13:46:38 -0700
Tonight 9p: Donald Rumsfeld on IRS, AP, and Benghazi. As political pressure mounts in the nation's capital, this evening "Piers Morgan Live" welcomes the return of Donald Rumsfeld, a man all too familiar with the red-hot glare accustomed to those ...
Fri, 10 May 2013 11:50:05 -0700
But Jack Monroe, a blogger who specialises in “austerity food”, can make them for just 9p. Now the single mother from Southend is to produce a book filled with more of her budget recipes after being handed a deal by Penguin. The offer came after her ...
Sun, 19 May 2013 17:07:54 -0700
... is good news for the Florida-based Championship Fighting Alliance promotion she fights for, and for the AXS TV cable network that recently secured the rights to broadcast her Friday fight against Allanna Jones (2-1) at Miami's Bank-United Center (9p.m.
Sun, 19 May 2013 04:59:57 -0700
... be sure to watch the hit series Bomb Girls. This week's episode, "Something Fierce" with guest star Rosie O'Donnell, airs again today at 12p ET/ 9a PT. As always, new episodes air Wednesdays at 9p ET/ 6p PT. Carry On. Wednesday starting at 9p E/ 6p ...
Sat, 18 May 2013 18:41:36 -0700
Although her ingredients come from the “value” range – which means a single veggie-burger of carrot, cumin and kidney-bean can cost as little as 9p – Jack claims her dishes are just as nutritious as those with more extravagant ingredients. She said: “I ...
Sat, 18 May 2013 05:00:43 -0700
... Restaurant” in 2011 and “Best European Restaurant” in Grand Rapids, according to Grand Rapids Magazine in 2012. The restaurant is located on Alpine Avenue and 6 mile and is open Tuesday-Thursday and Sunday 4-9p.m. and Friday-Saturday 4-10p.m.
Sat, 18 May 2013 22:21:42 -0700
Other events taking place over the next month. Table Quiz: Duffy's Cross on May 17th at 9p.m. Social Coffee Morning: Old School Kilcroney, on May 24th at 10am. Mini Marathon. The Flora women's 10k mini marathon will take place on Monday June 3rd 2013 ...
Thu, 16 May 2013 03:09:14 -0700
At the Moto garage on the M2 in Gillingham, known for having some of the most expensive fuel in the country, unleaded petrol was priced at £1.42.9p while diesel was going for £1.47.9p. Down the road at the Mace garage in Hoath Lane, drivers were paying ...
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