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Citrix XenApp
Developer(s) Citrix Systems
Stable release 5.0 / 2008-09-08; 15 months ago[1]
Operating system Microsoft Windows Server
Supported by v4.0
HP-UX - Solaris - AIX
Type Application Delivery
License Proprietary

Citrix XenApp (formerly Citrix MetaFrame Server and Citrix Presentation Server) is an application virtualization/application delivery product that allows users to connect to their corporate applications. XenApp can either host applications on central servers and allow users to interact with them remotely or stream and deliver them to user devices for local execution.


Technical Description

XenApp began life as an application hosting solution. Since 2007, XenApp has included application virtualization and streaming technologies that enable application delivery to user devices.


Network Protocol

The core XenApp application hosting technology utilizes Citrix Systems' proprietary presentation layer protocol or thin client protocol called Independent Computing Architecture (ICA).

Unlike framebuffered protocols like VNC, ICA transmits high-level window display information, much like the X11 protocol, as opposed to purely graphical information. The Citrix Display Driver is installed in Session Space and captures high level GDI draw commands, which can be replayed on GDI-capable clients, for example Windows-based clients. Clients are available for several operating systems, including Microsoft Windows (CE, 16-bit, 32-bit and 64-bit platforms), Mac OS, Linux, and other Unix-like systems.

Citrix MetaFrame version 3.x and 4.x servers listen for client connections on TCP port 2598, by default.[2][3] If the Session Reliability feature is disabled, then the server will listen on port 1494. Older MetaFrame servers (those running MetaFrame version 2.x or earlier) do not have the Session Reliability feature, and therefore always default to port 1494.

Both local and hosted application delivery methods in XenApp leverage existing network transmission protocols including TCP, HTTP, HTTPS, SMB and CIFS.

Server Components

The Citrix Developer Network contains a set of software development kits that enable custom development for XenApp. These SDKs include the following:

  • Citrix XenApp SDK
  • Citrix Virtual Channel SDK
  • Citrix ICA Client Object SDK
  • Citrix Web Interface SDK
  • Citrix Simulation API SDK

XenApp components, including application hosting servers, if any, reside on a Microsoft Windows computer, which can be either standalone or part of a larger cluster (farm) of Citrix servers. It is important to note that in addition to concurrent user Citrix licensing, there must exist a Terminal Server Client Access License (CAL) and a Windows Server CAL from Microsoft for each client connection. Both products must be adequately licensed for the environment to function correctly.

Client Components

There is a web-based Citrix client, freely available under the name Web Interface for XenApp. The Web Interface may be used as a secure ICA proxy over HTTPS when combined with Citrix Secure Gateway, both of which are included in the base XenApp product. XenApp also supports three UNIX variants: HP-UX, Solaris, and AIX which are included in Enterprise and Platinum editions of XenApp.

UNIX version

Presentation Server for UNIX is available for Solaris (SPARC and x86), AIX, and HP-UX. Patches typically come out first for the Solaris version. The product started as MetaFrame for Solaris 1.0 which was released in March 2000.[4] MetaFrame for UNIX (MFU) 1.1 added support for AIX and HP-UX and came out in the fall of that year and Feature Release 1 came out about a year later. The next version came out in the first half of 2003. It was originally planned as MFU 1.1 Feature Release 2 but was rebranded MetaFrame Presentation Server for UNIX 1.2.[5] However, references to MFU 1.1. FR2 can still be found (e.g. in the license key). Presentation Server for UNIX (PSU) 4.0 was released in the first half of 2005 and was the first version to be bundled with the Presentation Server suite.[6] Existing customers paying for upgrades and new versions (known as Subscription Advantage) can however continue to get just the UNIX version. Existing MFU 1.x installs cannot be upgraded to PSU4; instead a clean install is required.


Traditionally Citrix XenApp has faced minimal or no competition in the thin client computing space. But with Microsoft's new Terminal Services for Windows Server 2008, Microsoft Terminal Services is emerging as a clear competitor to XenApp at least in the small and medium business market space. Other XenApp competitors include Quest Software vWorkspace, Systancia AppliDis Fusion [7] and Ericom Software, and PowerTerm WebConnect. XenApp is built on top of the Windows Terminal Server platform which was originally developed by Citrix in the early-mid 90s. Win4Lin Virtual Desktop Server from Virtual Bridges provides similar functionality for serving sessions from Linux servers, while Sun's application virtualization offering, the Sun Secure Global Desktop, serves to provide a complete solution allowing for the delivery of both Windows and Unix applications on all major platforms.

See also


External links


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