Citrix Xenapp

Citrix XenApp 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.

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. 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 Citrix Xenapp.

Citrix also deals with Citrix Xenserver. You can Buy Software of these kinds online on many websites e.g. http://www.softwareforless.com/. Delivery Center, composed of Citrix XenDesktop, Citrix XenApp, Citrix XenServer and NetScaler, virtualizes servers, desktops and applications, centralizes them in the data center and broadcasts them as an on-demand service.