[THIN] KB: CTX113457 - Server-to-client Content Redirection Explained

CTX113457 - Server-to-client Content Redirection Explained

This document was published at: http://support.citrix.com/article/CTX113457

Document ID: *CTX113457*, Created on: Jun 26, 2007, Updated: Jun 26, 2007

Products: Citrix Presentation Server 4.5 for Windows Server 2003


*Summary*

There are two types of content redirection available with Citrix MetaFrame
Presentation Server 3.0 and later: Server-to-client and client-to-server.
This article describes server-to-client content redirection.

*Server-to-client content redirection*

Server-to-client content redirection refers to the redirection of URLs from
an ICA session to the client workstation to launch the local Web browser.
This can be done in an ICA-published application, a desktop session using
Program Neighborhood, or using Program Neighborhood Agent on the client
workstation.

Only the following types of content are redirected from the server to the
client workstation:

  • 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's Media Format)

*Server configuration*:

Content redirection can be configured on a per-server basis or at the farm
level in the Presentation Server Console/Access Management Console.

*Server-side changes*:

After installing Presentation Server, the following server-side registry
modifications are made:

The *HKEY_CLASSES_ROOT\<X>\shell\open\command* key (*<X>* can be either *
http*, *https*, *rtsp*, *rtspu*, *pnm*, or *mms*) is backed up to *
HKEY_LOCAL_MACHINE/Software/Citrix/FTABackup*.

Each key is modified as follows:

*Before Presentation Server is installed*:

The *http* key would look as follows:

HKEY_CLASSES_ROOT/http/Shell/Open/Command/"C:\Program Files\Internet
Explorer\iexplore.exe" -nohome

*After Presentation Server is installed*:

HKEY_CLASSES_ROOT/http/Shell/Open/Command/ "C:\Program
Files\Citrix\system32\*iexplore.exe*" %1

*The following procedure determines where Internet Explorer is launched from
*:

1. Enable server-to-client content redirection on the server.

2. Click on a supported content type (for example, a URL).

3. If the application containing the URL reads the HKEY_CLASSES_ROOT
registry key to determine which application to launch, a Citrix
iexplore.exeis launched, which is a 32-bit Windows, invisible,
windowed process. This
application receives the URL as a command line parameter as follows:

   1. It checks to see that the URL has a valid hostname.
      2. It checks to see that the user is not a console user.
      3. It checks to see that the user is in an ICA session.
      4. It checks to see if that the server is properly licensed.
      5. It checks to see if the particular content type is allowed
     to be redirected. See the *Advanced Setting
1<http://support.citrix.com/article/CTX113457&printable=true#P79_3833>
     * section below.
      6. It checks to see if the specified URL is in the Trusted List
     of allowed URLs. See the *Advanced Setting
2<http://support.citrix.com/article/CTX113457&printable=true#P88_5253>
     * section below.
      7. It checks to see if the passing of the URL to Wfshell is
     successful.

If any of the above checks fail, the Internet browser is launched on the
server.

4. Wfshell performs the following procedure, which either results in the
client successfully launching the Internet browser on the client or the
browser launching in the same ICA session at the server by Wfshell:

   1. It checks to see that the client connects and registers the
     capability to perform server-to-client content redirection.
      2. It sends the URL to the client to see if it can be launched.

5. The client undergoes the following procedure (if unsuccessful, Wfshell
tries to launch the Internet browser in the session):

   1. The client performs an HTTP ping of the URL on the client machine
     using MS Wininet. If the ping fails, Wfshell is notified.
      2. If the ping succeeds, the client tries to launch the URL at
     the client workstation. Which browser is launched is determined by the
     workstation's configuration. If the ping fails, the client
notifies Wfshell.
      3. If the ping succeeds, the client notifies Wfshell that it
     was able to launch the URL.

     Refer to the following graphic:

*Advanced settings for server-to-client content redirection*:

*Advanced setting 1*: The following setting adds the ability to configure
which server-to-client content redirection file types can be redirected.

By default, server-to-client content redirection redirects all or none of
the file types (http, https, rtsp, rtspu, pnm, and mms).

*WARNING! *Using Registry Editor incorrectly can cause serious problems that
may 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.

A registry key is specified to allow certain file types to be excluded from
content redirection. If HKEY_LOCAL_MACHINE \SOFTWARE\Citrix\SFTA
\DisableServerFTA is set, the multiple-string registry value
HKEY_LOCAL_MACHINE\SOFTWARE \Citrix\SFTA\NoRedirectClasses specifies which
file types are excluded from redirection. If the file type is not in the
list, it is redirected.

To implement this enhancement, make the following value changes to the
registry key using Registry Editor:

HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\SFTA*
Name*: DisableServerFTA*
Type*: REG_DWORD*
Value*: 1*

Name*: NoRedirectClasses*
Type*: REG_MULTI_SZ*
Value*: Specify any combination of the following values:
http,https,rtsp,rtspu,pnm,mms (these values are comma-delimited with no
space between)

With these registry changes, administrators can configure which file types
to exclude when using server-to-client content redirection.

*Advanced setting 2*:* *This setting allows redirection of specific URLs
from server to client without redirecting other URLs.

The HKEY_LOCAL_MACHINE \SOFTWARE\Citrix\SFTA\ValidSites registry key lets
you specify URLs to be redirected from server to client.

To implement this enhancement, make the following value change to the
registry using Registry Editor:

HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\SFTA*
Name*: ValidSites*
Type*: MULTI STRING*
Value*: *www.my_url.com
<http://support.citrix.com/article/www.my_url.com>*(specify the URLs)

*Note*: The asterisk (*) is supported as a wildcard character.

*Server-to-client content redirection troubleshooting*:

   1. Determine if the problem only occurs when redirecting from the
     application, or if it occurs in general. Go to *Start > Run* and
     type the URL.
      2. If the URL works, there may be a problem with how the
     application is trying to launch the link or with Citrix
     iexplore.exe.
      3. Determine if the application is reading the *Shell
Open*command. Temporarily change the
     iexplore.exe Shell Open value to a bogus filename. If this
     fails, the application is reading this registry value. There is
a problem on
     the client side or with iexplore.exe.
      4. On the client, does the URL work if you open a browser and
     type the same URL?
      5. Is there a proxy between the server and the client?
      6. If you do not want to use server-to-client content
     redirection (for example, if there is an application that cannot
launch the
     Web browser correctly because it has unique command line
parameters that it
     is trying to pass), the feature can be disabled through the following
     registry setting:

     HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\SFTA*
     Name*: DisableServerFTA*
     Type*: DWORD*
     Value*: 1


--
Jim Kenzig
Microsoft MVP - Terminal Services
http://www.thinhelp.com
Citrix Technology Professional
Provision Networks VIP
CEO The Kenzig Group
http://www.kenzig.com
Blog: http://www.techblink.com

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