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Host to client redirection

January 18, 2019
Contributed by: 
C

Content redirection allows you to control whether users access information by using applications published on servers or applications running locally on user devices.

Host to client redirection is one type of content redirection. It is supported only on Server OS VDAs (not Desktop OS VDAs).

  • When host to client redirection is enabled, URLs are intercepted at the server VDA and sent to the user device. The web browser or multimedia player on the user device opens these URLs.
  • If you enable host to client redirection and the user device fails to connect to a URL, the URL is redirected back to the server VDA.
  • When host to client redirection is disabled, users open the URLs with web browsers or multimedia players on the server VDA.
  • When host to client redirection is enabled, users cannot disable it.

Host to client redirection was previously known as server to client redirection.

When to use host to client redirection

You might consider using host to client redirection in specific but uncommon cases, for performance, compatibility, or compliance. Normally, other forms of content redirection are better.

Performance:

You can use host to client redirection for performance, so that whenever an application is installed on the user device, it is used in preference to an application on the VDA.

Keep in mind that host to client redirection improves performance only under specific conditions, because the VDA already optimizes Adobe Flash and other types of multimedia content. First, consider using the other approaches (policy settings) noted in the tables in this article, rather than host to client redirection. Those settings offer more flexibility and usually give a better user experience, particularly for less-powerful user devices.

Compatibility:

You can use host to client redirection for compatibility in the following use cases:

  • You use content types other than HTML or multimedia (for example, a custom URL type).
  • You use a legacy media format (such as Real Media) that is not supported by the VDA multimedia player using multimedia redirection.
  • The application for the content type is used by only a few users who already have the application installed on their user device.
  • The VDA cannot access certain websites (for example, websites internal to another organization).

Compliance:

You can use host to client redirection for compliance in the following use cases:

  • The application or content licensing agreement does not permit publishing via the VDA.
  • Organizational policy does not permit a document being uploaded to the VDA.

Some situations are more likely in complex environments, and also if the user device and the VDA belong to different organizations.

User device considerations

Environments can have many different types of user devices.

User device Situation or environment Content redirection approach
Tablet - Any approach (see next table)
Laptop PC - Any approach (see next table)
Desktop PC Users use a wide range of apps installed on the user device Any approach (see next table)
Desktop PC Users use only a few known apps that are installed on the user device Local App Access
Desktop PC Users use no apps installed on the user device Multimedia redirection and/or Flash redirection
Desktop appliance Vendor supports multimedia redirection and/or Flash redirection Multimedia redirection and/or Flash redirection
Thin client Vendor supports multimedia redirection, Flash redirection, and host to client redirection Any approach (see next table)
Zero client Vendor supports multimedia redirection and/or Flash redirection Multimedia redirection and/or Flash redirection

Use the following examples to help guide your content redirection approach.

URLs link Situation or environment Content redirection approach
Webpage or document The VDA cannot access the URL Host to client redirection
Webpage The webpage contains Adobe Flash Flash redirection
Multimedia file or stream The VDA has a compatible multimedia player Multimedia redirection
Multimedia file or stream The VDA does not have a compatible multimedia player Host to client redirection
Document The VDA does not have an application for that document type Host to client redirection
Document Do not download the document to the user device No redirection
Document Do not upload the document to the VDA Host to client redirection
Custom URL type The VDA does not have an application for that custom URL type Host to client redirection

Citrix Receiver for Windows, Citrix Receiver for Mac, Citrix Receiver for Linux, Citrix Receiver for HTML5, and Citrix Receiver for Chrome support Host to client redirection.

To use host to client redirection, the user device must have a web browser, multimedia player, or other application that is suitable for the content. If the user device is a desktop appliance, thin client, or zero client, confirm that it has suitable applications and is sufficiently powerful.

User devices enabled for Local App Access use a different mechanism for content redirection, and do not require host to client content redirection.

You can use Citrix policies to prevent host to client content redirection for unsuitable devices.

How users experience host to client redirection

Host to client redirection is used when URLs are:

  • Embedded as hyperlinks in an application (for example, in an email message or document).
  • Selected through VDA application menus or dialogs, if the application uses the Windows ShellExecuteEx API.
  • Typed in the Windows Run dialog.

Host to client redirection is not used for URLs in a web browser (either in a webpage or typed in the address bar of the web browser).

Note

If users change their default web browser on the VDA (for example, using Set Default Programs), that change can interfere with host to client redirection for applications.

When host to client content redirection is enabled, the app that opens the URL depends on the configuration of the user device for the URL type and the content type. For example:

  • An HTTP URL that has an HTML content type opens in the default web browser.
  • An HTTP URL that has a PDF content type might open in the default web browser, or it might open in another application.

Host to client content redirection doesn’t control this user device configuration. If you do not control the configuration of the user device, consider using Flash redirection and multimedia redirection, rather than host to client content redirection.

The following URL types are opened locally through user devices when host to client redirection is enabled:

  • HTTP (Hypertext Transfer Protocol)
  • HTTPS (Secure Hypertext Transfer Protocol)
  • RTSP (Real Player and QuickTime)
  • RTSPU (Real Player and QuickTime)
  • PNM (Legacy Real Player)
  • MMS (Microsoft Media Format)

You can change the list of URL types for host to client redirection, to remove and add URL types, including custom URL types.

Enable host to client redirection

Enabling host to client redirection starts by enabling a Citrix policy setting.

The Host to client redirection policy setting is located in the File Redirection policy settings section. By default, this setting is disabled.

In addition, you might need to set registry keys and Group Policy for the server VDAs, depending on the VDA OS.

  • If the server VDA is Windows Server 2008 R2 SP1, you do not need to set registry keys or Group Policy.
  • If the server VDA is Windows Server 2012, Windows Server 2012 R2, or Windows Server 2016, you must set registry keys and Group Policy.

Warning

Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

Registry changes

  1. Copy the text between Reg file start and Reg file end below, and paste it in Notepad.
  2. Save the Notepad file using Save As as type All Files and the name ServerFTA.reg.
  3. Distribute the ServerFTA.reg file to the servers using Active Directory Group Policy.
--  Reg file start --

Windows Registry Editor Version 5.00


[HKEY_CLASSES_ROOT\ServerFTAHTML\shell\open\command]

@="\"C:\\Program Files (x86)\\Citrix\\system32\\iexplore.exe\" %1"


[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ServerFTA]

@="ServerFTA"


[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ServerFTA\Capabilities]

"ApplicationDescription"="Server FTA URL."

"ApplicationIcon"="C:\\Program Files (x86)\\Citrix\\system32\\iexplore.exe,0"

"ApplicationName"="ServerFTA"



[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ServerFTA\Capabilities\URLAssociations]

"http"="ServerFTAHTML"

"https"="ServerFTAHTML"



[HKEY_LOCAL_MACHINE\SOFTWARE\RegisteredApplications]

"Citrix.ServerFTA"="SOFTWARE\\Citrix\\ServerFTA\\Capabilities"

-- Reg file end -- ---

Group Policy changes

Create an XML file. Copy the text between xml file start and xml file end the example, paste it in the XML file, and then save the file as ServerFTAdefaultPolicy.xml.

-- xml file start --

<?xml version="1.0" encoding="UTF-8"?>

<DefaultAssociations>

<Association Identifier="http" ProgId="ServerFTAHTML" ApplicationName="ServerFTA" />

<Association Identifier="https" ProgId="ServerFTAHTML" ApplicationName="ServerFTA" />

</DefaultAssociations>

-- xml file end -- ---

From the current Group Policy management console, navigate to: Computer configuration > Administrative Templates > Windows Components > File Explorer > Set a default associations configuration file, and provide the ServerFTAdefaultPolicy.xml file you created.

Change the list of URL types for host to client redirection

To change the list of URL types for host to client redirection, set the following registry key on the server VDA.

Key: HKLM\Software\Wow6432Node\Citrix\SFTA

To delete URL types from the list, set DisableServerFTA and NoRedirectClasses:

Name: DisableServerFTA

Type: REG_DWORD

Data: 1

Name: NoRedirectClasses Type: REG_MULTI_SZ Data: Specify any combination of the values: http, https, rtsp, rtspu, pnm, or mms. Type multiple values on separate lines. For example:

http

https

rtsp

To add URL types to the list, set ExtraURLProtocols:

Name: ExtraURLProtocols

Type: REG_MULTI_SZ

Data: Specify any combination of URL types. Each URL type must include the :// suffix; separate multiple values by using semicolons. For example:

customtype1://;customtype2://

Enable host to client redirection for a specific set of websites

To enable host to client redirection for a specific set of websites, set the following registry key on the server VDA.

Key: HKLM\Software\Wow6432Node\Citrix\SFTA

Name: ValidSites

Type: REG_MULTI_SZ

Data: Specify any combination of fully qualified domain names (FQDNs). Type multiple FQDNs on separate lines. An FQDN can include a wildcard in the leftmost position only. This matches a single level of domain, which is consistent with the rules in RFC 6125. For example:

www.example.com

*.example.com

Host to client redirection
January 18, 2019
Contributed by: 
C
January 18, 2019
Contributed by: 
C

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