View source for NX technology

{{short description|Desktop virtualization and application delivery software}}
{{distinguish |NX (software)|NX bit}}
{{Multiple issues|
{{primary sources|date=January 2013}}
{{Advert|date=April 2017}}
}}

{{Infobox software
| name                   = NoMachine
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| released               = 2003<!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} -->
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| latest release version = 8.10.1
| latest release date    = {{Start date and age|2023|11|06|df=yes/no}}
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| size                   = 28 [[Megabyte|MB]]
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| genre                  = [[Remote desktop]] software
| license                = [[Freeware]]
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| website                = {{URL|https://www.nomachine.com/}}
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'''NX technology''', commonly known as ''NX'' or NoMachine, is a remote access and remote control computer software, allowing remote desktop access and maintenance of computers.<ref>{{Citation|language=en|title=NoMachine – Remote desktop based on NX technology|url=https://www.itsmdaily.com/nomachine-remote-desktop-based-on-nx-technology/|website=ITSM daily|date=2019-03-28|access-date=2023-06-14|author=Vladimir Blagojevic|archive-date=September 27, 2022|archive-url=https://web.archive.org/web/20220927024918/https://www.itsmdaily.com/nomachine-remote-desktop-based-on-nx-technology/|url-status=live}}</ref> It is developed by the [[Luxembourg]]-based company NoMachine S.à r.l.. <ref>{{Citation | url = https://www.nomachine.com/ | title = NoMachine}}.</ref> NoMachine is proprietary software and is free-of-charge for non-commercial use.<ref>{{Citation|language=en|title=NoMachine review—versatile free remote desktop access|url=https://www.techradar.com/reviews/nomachine-review|website=TechRadar|date=2020-04-03|access-date=2023-06-14|author=Daniel Blechynden|archive-date=March 14, 2022|archive-url=https://web.archive.org/web/20220314021806/https://www.techradar.com/reviews/nomachine-review|url-status=live}}</ref>

== History ==
NX's design was derived from the Differential X Protocol Compressor project (DXPC). In 2003, the compression and transport protocol NX was created to improve the performance of the [[X_Window_System|native X display protocol]] so it could be used over slow connections such as dial-up modems. It wrapped remote connections in [[Secure Shell|SSH]] sessions for encryption. The core compression technology was released under the GNU [[GNU General Public License|GPL2]] license (NX 1) for Linux servers on February 14, 2003,<ref>{{Citation | url = https://developers.slashdot.org/story/03/09/26/1242200/proxy-servers-lighten-up-x  | publisher = Slashdot | title = Proxy Servers Lighten Up X}}</ref> whilst other components such as the NX Server and NX Client programs remained proprietary.<ref>{{Citation|language=en|title=Linux in Government: Major Breakthrough in Linux Technology|url=https://www.linuxjournal.com/article/8342|website=Linux Journal|date=2005-06-06|access-date=2023-06-14|author=Tom Adelstein|archive-date=April 8, 2022|archive-url=https://web.archive.org/web/20220408063854/https://www.linuxjournal.com/article/8342|url-status=live}}</ref> The last update to this open-source version was released in 2012. In 2010, the company announced they would be releasing the technology under a proprietary license.<ref>{{Citation | url = https://it.slashdot.org/story/10/12/21/2354254/nx-compression-technology-to-go-closed-source  | publisher = Slashdot | title = NX Compression Technology To Go Closed Source}}</ref> In 2013, NX became closed-source<ref>{{Citation | url = https://searchvirtualdesktop.techtarget.com/tip/Delivering-remote-Mac-Linux-and-Windows-desktops-with-NoMachine-NX | publisher = brianmadden.com | title = Delivering remote Mac, Linux and Windows desktops with NoMachine NX}}</ref> and it was in 2013 that NX software became NoMachine software.

== Features ==
NoMachine is available for most [[Desktop computer|desktop computers]] with common operating systems, including [[Microsoft Windows]] and [[Windows Server]], as well as Apple's [[macOS]].<ref>{{Citation|language=en|title=NoMachine for Mac|url=https://mac.softpedia.com/get/Internet-Utilities/NoMachine-NX.shtml|website=Softpedia|access-date=2023-06-14|author=Sergiu Gatlan|archive-date=April 30, 2017|archive-url=https://web.archive.org/web/20170430094301/https://mac.softpedia.com/get/Internet-Utilities/NoMachine-NX.shtml|url-status=live}}</ref> There are also packages for several Linux distributions and derivatives, for example, Debian, Ubuntu,<ref>{{Citation|language=en|title=Install NoMachine RDP on Ubuntu|url=https://computingforgeeks.com/install-nomachine-rdp-tool-on-ubuntu-linux/|website=Computing for Geeks|date=2022-07-02|access-date=2023-06-14|author=Josphat Mutai|archive-date=July 11, 2022|archive-url=https://web.archive.org/web/20220711220110/https://computingforgeeks.com/install-nomachine-rdp-tool-on-ubuntu-linux/|url-status=live}}</ref> Red Hat, CentOS<ref>{{Citation|language=en|title=Install and Use NoMachine Remote Desktop on CentOS|url=https://www.howtoforge.com/install-and-use-nomachine-on-centos-8/|website=HowtoForge|access-date=2023-06-14|author=Hitesh Jethva|archive-date=March 24, 2023|archive-url=https://web.archive.org/web/20230324022016/https://www.howtoforge.com/install-and-use-nomachine-on-centos-8/|url-status=live}}</ref> and Fedora Linux. There is also a version which can run on distribution variants for Linux ARM devices, including Raspberry Pi OS.<ref>{{Citation|language=en|title=Using NoMachine on the Raspberry Pi|url=https://pimylifeup.com/raspberry-pi-nomachine/|website=PiMyLifeUp|date=2023-03-01|access-date=2023-06-14|author=Emmet|archive-date=April 15, 2023|archive-url=https://web.archive.org/web/20230415060305/https://pimylifeup.com/raspberry-pi-nomachine/|url-status=live}}</ref> An app is available which allows users to connect from smartphones and tablets running Android or Apple's iOS/iPadOS operating system.

NoMachine Terminal Server Family for Linux also offers the ability to run multiple virtual Linux desktops on a Linux server which are remotely accessed over a network connection. Images rendered on the server are compressed and encoded and then sent to the client for decryption and decompression. NX utilizes uses a combination of video and image encoding based on standard codecs and a number of techniques developed by NoMachine as well as [[VirtualGL]] to access high-end [[OpenGL]]-based [[X Window System|X11]] applications and 3D [[Computer-aided design|CAD]] programs.

== NoMachine NX 4 and later versions ==
NoMachine's NX technology uses optimal image compression and caching with the latest video-encoding techniques. When connecting hosts across the network, the NX protocol works as a generic tunnel, with additional framing and flow control information, and dynamically adapts compression and bandwidth according to network speed and capacity. The display protocol uses a combination of video and image encoding, based on standard codecs and a number of techniques developed by NoMachine. NX monitors display and user activity to adapt quality and buffering to the displayed application.

== Authentication ==
From version 4.0 on, when the default NX protocol is used, the login can be via password-based authentication, private key or [[Kerberos (protocol)|Kerberos]] ticket authentication.

When NX is configured to send its data by [[SSH File Transfer Protocol|SSH]] (available only on enterprise-version servers), the following authentication methods are available:

'''Client to Server'''

* NX login as NX user using the NX SSH key and user password-based authentication
* System login with password-based authentication
* System login with SSH key-based authentication
* System login with SSH key-based authentication and SSH key stored on a smart card
* System login with Kerberos ticket existing on client side
Server to Node

* Login with password
* Login with SSH key forwarded from client (e.g. NoMachine Player) via server to node
* Login with Kerberos ticket forwarded from client via server to node
* Login with Kerberos ticket requested by Kinit on server host
* Login with Kerberos ticket requested by [[Pluggable authentication module|PAM]] module on server host.
* Login with password to Kerberos ticket requested by PAM module on node host

== Legacy technology ==
NX [[Data compression|compresses]] the X11 data to minimize the amount of data transmitted, and [[Cache (computing)|caches]] data to keep the session as responsive as possible. For example, the first time a menu is opened, it may take a few seconds, but is subsequently almost instant.

NX is faster than its predecessors, as it eliminates most of the X [[Round-trip delay time|round trips]], while dxpc and MLView only compress data.

The two principal components of NX are '''nxproxy''' and '''nxagent'''. nxproxy is derived from [[dxpc]] and is started on both the remote (client in X terminology) and local (server in X terminology) machines, simulating an X server on the client and forwarding remote X protocol requests to the local X server.

Simplest setup:<ref name="NX build">{{cite web |url= https://www.nomachine.com/DT12I00020|title= Building and using NX components |publisher=NoMachine |date=2015-05-22 |access-date= 2015-08-21}}</ref>

 remote clients (xterm, etc.)
             ↕
       nxproxy client
             ↕
          Network
             ↕
       nxproxy server
             ↕
 local X server (monitor/keyboard)

'''nxproxy''' alone achieves 1:10 to 1:1000 compression ratios,<ref>{{Citation | publisher = NoMachine | url = http://www.nomachine.com/documentation/building-components.php | title = Building and using NX components}}.</ref> reducing bandwidth, but does not eliminate most of X's synchronous round trips, responsible for most of X's perceived latency.

'''nxagent''', derived from Xnest (similar to [[Xephyr]]), is typically started on the remote (client) machine, thus avoiding most X11 protocol round trips. Together with nxproxy (built into nxagent), this setup performs well over low-bandwidth and high-latency links.

Typical setup:<ref name="NX build"/>

  remote clients (xterm, etc.)
             ↕
   nxagent server side \
   nxagent client side   nxagent executable
      nxproxy client   /
             ↕
          Network
             ↕
       nxproxy server
             ↕
 local X server (monitor/keyboard)

On systems with a functional X11 implementation, nxproxy and nxagent are all that is needed to establish a connection with low-bandwidth requirements between a set of remote X clients and the local X server. SSH can be used to establish a secure tunnel between the hosts. NX 3 relies on SSH functionalities and existing open-source SSH software, making it possible to run contemporary Unix and Windows desktops and arbitrary network applications over the Internet in a secured and controlled way.

FreeNX and the various NX Clients are used for setup, handling suspend and resume, secure tunnelling over SSH, and printing and sound.

== Other display protocols ==
NoMachine's NX protocol allow client connections to hosts via [[Remote Desktop Protocol]] (for Windows Remote Desktop Services sessions) and remote [[Virtual Network Computing]] sessions (most modern general-purpose operating system platforms), as well as XDM.

== NX derivatives and forks ==
Prior to version 4.0, NoMachine released core NX technology under the [[GNU General Public License]], and offered [[non-free software|non-free]] commercial NX solutions,<ref>{{Citation | url = http://www.nomachine.com/enterprise | publisher = NoMachine | type = product details | title = NX Terminal Server and Remote Access Software}}.</ref> free client and server products for [[Linux]] and [[Solaris (operating system)|Solaris]], and free client software for [[Microsoft Windows]], [[macOS]] and [[embedded system]]s.

Due to the free-software nature of older NX releases, the FreeNX project was started to provide wrapper scripts for the GPL NX libraries.<ref>{{cite web |url= http://freenx.berlios.de/ |title= FreeNX – the free NX |publisher= Berlios |place= [[Germany|DE]] |access-date= 2014-02-14 |archive-url= https://web.archive.org/web/20131111173425/http://freenx.berlios.de/ |archive-date= 2013-11-11 |url-status= dead }}</ref> FreeNX was developed and maintained by [[Fabian Franz]], but has not announced a release since 2008.<ref>{{Citation | place = DE | url = http://developer.berlios.de/projects/freenx/ | title = FreeNX | type = project page | publisher = Berlios}}.</ref>

[[2X Software]] has developed another commercial [[terminal server]] for Linux using the NX protocol.<ref>{{cite web|url=http://www.2x.com/terminalserver/features/ |title=2X TerminalServer for Linux Features |publisher=2X |access-date=2016-03-30 |url-status=dead |archive-url=https://web.archive.org/web/20120116195444/http://www.2x.com/terminalserver/features/ |archive-date=January 16, 2012 }}.</ref>

On July 7, 2009, [[Google]] announced their open-source NX server, [[Neatx]], as an internal project.<ref>{{Citation | contribution-url = http://google-opensource.blogspot.com/2009/07/releasing-neatx-open-source-nx-servier.html | type = [[World Wide Web]] log | date = Sep 2009 |  title = Open source | publisher = Google | contribution = Releasing Neatx, an Open Source NX Server}}.</ref> {{Which |date=October 2015}} The project had no releases and is not actively developed. Its source code is available under the GNU GPL v2 license.<ref>{{Citation | contribution-url = http://code.google.com/p/neatx/ | contribution = Neatx | publisher = Google | title = Code}}.</ref>

[[X2Go]] is based on the 3.x NX libraries, but is not compatible with other implementations.<ref>{{cite web |url= http://x2go.org/ |title= X2Go – everywhere@home | date= 2013-12-28 |access-date= 2014-02-14}}</ref><ref>{{Citation | url = http://wiki.x2go.org/doku.php/doc:faq:start | publisher = X2go | title = FAQ}}.</ref>  The client and server are released under a combination of GNU GPLv2 or later, and GNU AGPLv3 or later.<ref>{{Citation | url = http://wiki.x2go.org/doku.php/sources:start#licenses_of_x2go | publisher = X2go | title = License information}}.</ref>

== Clients ==
The primary NX clients are the official freeware, NoMachine, and NoMachine Enterprise Client. Several [[open-source software|open-source]] projects can also use the NX protocol but many of these OSS projects do not work with more recent versions of the official NX software.

An OS mature project was Lawrence Roufail's ''nxc'' client library, a full library which can be used for other clients to build upon. The ''nxrun'' application utilizes this library. {{asof|2006}}, the library does not allow suspending or resuming sessions, and uses only [[JPEG]] graphics compression.

The ''kNX'' project was a proof-of-concept application written by Joseph Wenninger, with plans for it to eventually become a complete NX client to show that an open-source client could be written. Its development was halted before it was completed. In late 2005, [[Fabian Franz]] and George Wright began modifying kNX to use the nxc library, but abandoned the project.

More recent open-source efforts include ''QtNX'', which offers full suspend and resume. However, it has been reported as incompatible with the most recent NX libraries.

''Nxcl, a''n update to nxclientlib, the core of QtNX, was completed by Seb James in September 2007, and works with version 3 of the NX core libraries.{{Citation needed |date=August 2008}} It also drops dependency on Qt, which prevented nxclientlib from becoming widely used as a cross-platform basis for NX client programs. nxcl provides a library that can be linked to a client program (libnxcl), and a self-contained NX client with a [[D-Bus]] [[API]] (the nxcl binary). It is available from the FreeNX [[Subversion (software)|Subversion]] server.

Another obsolete (last updated Jan 2013) OSS NX client is ''OpenNX'', described as a "drop-in replacement for NoMachine's [proprietary] nxclient" with full suspend and resume.

Various open-source terminal server projects, such as [[X2Go]], also use the NX protocol. However, X2Go is not compatible with other NX servers or clients.

[[Remmina]], another recent GTK+ remote desktop client project, announced the ability to use the NX protocol in its release 0.8.

== Previous X11 compression schemes ==
* [[Low Bandwidth X]] (lbxproxy; obsolete and of historical interest only)

== See also ==
* [[Comparison of remote desktop software]]
* [[GNU Screen]]{{snd}} a terminal multiplexer for console-mode (text-mode) applications
* [[Xpra]]{{snd}} a system for attaching and detaching remote X programs
* [[xmove]]{{snd}} a tool allows you to move programs between X Window System displays (outdated)

== References ==
{{Reflist|30em}}

== External links ==
* {{Official website|https://www.nomachine.com/}}
* [https://wiki.x2go.org/doku.php/doc:newtox2go X2Go] X2Go Introduction Page
* [https://web.archive.org/web/20050803005415/http://freenx.berlios.de/ FreeNX]  project page on [[BerliOS]].
* [https://wiki.archlinux.org/index.php/FreeNX FreeNX] project page at [[Arch Linux]].
* [http://opennx.sourceforge.net/ OpenNX] project page, [http://sourceforge.net/projects/opennx/ SourceForge].
{{Remote administration software}}

[[Category:Remote desktop]]
[[Category:Linux windowing system-related software]]
[[Category:Formerly open-source or free software]]
[[Category:Remote desktop software for Linux]]