About XenApp

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.

XenApp began life as an application hosting solution. Only since 2007 has XenApp included application virtualization and streaming technologies that enable application delivery to user devices. The core XenApp application hosting technology utilizes Citrix Systems' proprietary presentation layer protocol or thin client protocol called Independent Computing Architecture (ICA). The Microsoft Remote Desktop Protocol, part of Microsoft's Terminal Services, is based on Citrix technology and was licensed from Citrix in 1997. [2]

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. [3][4] 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.

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.

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.
[edit] 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.[5] 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.[6] 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.[7] 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.