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Application Launching and Embedding with NFuse 1.5

As I have already mentioned, Citrix provides two ways of running applications through an NFuse-enabled Web site. The first uses an ALE client to access an application embedded in a Web page, and the other uses a regular ICA client's "helper" application to launch an application from the NFuse Web page.

Application Launching

As the name suggests, in this scenario, the Web page is used only as a means of providing a link to a published application in a Citrix farm. Once clicked, the application is "launched" and runs in a separate window independently of the browser. The user is free to surf to a different Web site or even to close the browser down completely, and the launched application will remain active until the user explicitly closes it. Figure 2 shows an example of MS Word, launched from a link on my sample NFuse Web site.

Figure 2

Microsoft Word launched from a Web page

Launching is the default choice for running an application when building a Web site using the Citrix Web Site Wizard. Figure 3 shows this selection along with the Use Seamless If Available option. Running an application within a seamless window is currently supported only with the Win32 ICA client. All other clients will simply ignore this option and run the launched application within an ICA client window.

Figure 3

Selecting application launching in the Web Site Wizard

The NFuse-generated HTML link for an application that is being launched will look similar to the following:

<font size=-1><b><a href="launch.asp?NFuse_Application=MSx0020Word&NFuse_MIMEExtension=.ica" TARGET="hiddenwindow">
<IMG SRC="iconfilename" border=0 alt="MS Word" align=left hspace=3>
MS Word<br>
</a></b></font>

Notice the reference to the launch.asp script. This script is responsible for initiating the construction of the corresponding ICA file for the application and its subsequent insertion into the HTML text stream that is returned to the user's browser. When the client browser receives this ICA file, the associated ICA client uses it to launch the application on the specified server. For more information on the individual scripts that compose an NFuse site, please refer back to the article "Citrix NFuse 1.5: Part 1 – Basic Setup and Configuration."

NFuse supports only a subset of the available ICA clients for application launching. A client qualifies only if it can be executed from within a Web browser. This excludes the WinCE, EPOC, and DOS clients. All other clients are supported—these are summarized in Table 1 along with their minimum required version number.

Table 1

Minimum Required ICA Client Versions for Application Launching with NFuse

ICA Client

Minimum Version Number

Win32

4.21.779

Win16

4.20.779

Macintosh

4.10.23

Linux

3.0

UNIX

3.0.85

Java application

4.11

The only thing required to use a supported ICA client for application launching is to install it on the client computer, with the exception of the Java and Macintosh clients, which require some additional browser configuration. Chapter 3, "Configuring ICA Client Devices" in the Citrix NFuse 1.5 Administrators Guide, explains exactly what changes need to be made for these clients.

For those of you familiar with NFuse 1.0, you will notice that NFuse 1.5 has the same client version requirements. This is not a typo, and contrary to what you may think, a 6.0 ICA client is not required for a user to be able to launch applications from an NFuse 1.5-enabled Web server. This even includes the situation in which you may be using session ticketing to provide enhanced user authentication security. Session ticketing is actually a server-side enhancement and does not require an updated client to function. I will look more closely at the session ticketing option in the third article in this series, “Citrix NFuse 1.5: Part 3 - Security.

Of course, if you are looking to utilize some of the client enhancements such as increased screen resolution or color depth, then you will want to look at using a 6.0 client. For strong ICA connection encryption, you can look to use a 6.0 client, where strong encryption support is now a standard option, or you can use the corresponding SecureICA version for the client, listed in Table 1.

One of the reasons that I think confusion exists around the required client version has to do with the default behavior for the new Client Detection and Installation (CDI) feature, which is automatically included if you generate a Web site from the Citrix Web Site Wizard. CDI will pop up a message recommending a client upgrade or installation if it cannot verify that a 6.0 client is already installed. Although this may certainly be helpful in a new or Internet-based NFuse implementation, for an administrator looking to integrate NFuse into an existing environment, it may prove to be an unnecessary support issue. I will be looking more closely at CDI later in this article.

Application Embedding

Unlike application launching, in which the Web browser is used only as the vehicle for accessing the user's application list, when an application is embedded, it's actually placed within the confines of a Web page itself. In this scenario, the Web browser and the application are tightly coupled. If within the browser session containing the application, the user surfs to another Web site, selects an alternate application to load, or shuts down the browser, the currently active application session is immediately disconnected. Figure 4 demonstrates MS Word embedded within the Web page containing the application list.

Figure 4

MS Word embedded in a Web page

In the Web Site Wizard, the option to embed an application is made on the same screen as the launching option (see Figure 5). One of the things you will notice is that when the Embedded in a Web Page option is selected, only one of the three ALE client types can be chosen. NFuse can support multiple ALE clients, but this does require manual scripting for the browser to select the appropriate client to use. Typically, if you are going to be providing support for more than one simultaneous type of browser, then the Java applet option provides the most flexibility because it will work with any browser that supports Java Development Kit (JDK) 1.1. The one downside to this is that the applet must be downloaded and run each time a user connects to the application, unlike the ActiveX and plug-in controls, which are downloaded once and then remain on the client.

Figure 5

Selecting application embedding in the Web Site Wizard

The HTML that is generated for an individual user's embedded application list is slightly different than the equivalent list of launched applications. For example, the HTML to launch MS Word embedded within the browser would look similar to the following:

<font size=-1><b><a href="appembed.asp?NFuse_Embedmethod=1&NFuse_Application=Microsoftx0020Wordx00202000" target="wpn_embed">

<IMG SRC="/NFuseIcons/Microsoftx0020Wordx00202000_971907750.gif" border=0 alt="Microsoft Word 2000" align=left hspace=3>
Microsoft Word 2000<br>
</a></b></font>

The appembed.asp script's main function is to input the appropriate text into the HTML text stream, depending on the target ALE client. For example, if the ALE client were the Java applet, then the text would look similar to the following:

<APPLET 
    codebase='/NFuseClients/en/icajava/'
    code='com.citrix.JICA.class' 
    WIDTH=640 HEIGHT=480
    archive='netscape/JICAN.jar'>
        <PARAM NAME=cabbase VALUE='ie/JICAM.cab'>
        <param name=Start value='Auto'>
        <param name=icafile value="launch.asp?NFuse_Application=MSx0020PowerPointx00202000">

        <param name="password" value="plain text password">

        <param name=client.wfclient.usehostname value='no'>
        <param name=client.wfclient.clientname value='NRSC-twmathers'>
</APPLET>

Within this text, you can see that it also makes use of the launch.asp script to populate the icafile parameter for the ALE client. More information on the individual scripts can be found in the article "Citrix NFuse 1.5: Part 1 – Basic Setup and Configuration."

As I mentioned earlier, there are four different types of ALE clients. Table 2 shows the available ALE clients and their minimum version required to function with NFuse 1.5. Like the traditional ICA clients, NFuse 1.5 supports any ALE client that is supported by NFuse 1.0.

Table 2

Minimum Required ALE Client Versions for Application Embedding with NFuse

ICA Client

Minimum Version Number

ActiveX

4.20.779

32-bit plug-in

4.20.779

16-bit plug-in

4.20.779

Java applet

4.11

ALE Client Installation

With previous versions of the ALE clients, you could download the installation files independently of the full ICA client installation. For example, the 4.21.779 version of the ActiveX client is downloadable as a signed CAB file that contains the OCX control, the wfica32.exe helper application, and the strong encryption DLLs. This file could be used to automatically install the ActiveX control on a client's machine without requiring any user input. Citrix does include a WFICA.CAB file as part of its 6.0 Web-based client install, but this is the full ICA 32-bit client, not simply the 6.0 ActiveX control.

A similar situation exists for the plug-ins. WFPlug16 and WFPlug32 executables are downloadable from the Citrix Web site and can be used to install the 4.21.779 plug-ins. Equivalent 6.0 installation packages are not available, and instead require that the full 32- or 16-bit clients be installed.

The only individual 6.0 ALE client installation package available is the Java applet. This is necessary, of course, because the Java applet is automatically downloaded and run on the user's browser whenever an application configured to run with the Java ALE client is accessed.

ALE ICA Client File Security

When a user first starts an embedded application using either the ActiveX control or a Netscape plug-in, and when the MetaFrame server has client drive mapping enabled, the user will see the dialog box shown in Figure 6.

Figure 6

The ALE ICA Client File Security dialog box

This enables the user to specify what access that published application (and possibly others) on that specific server will have to the user's local client drives. This prompt appears only when accessing an embedded application and does not appear if an application is being launched.

The first time that the security dialog box appears, if it does not already exist, the file webica.ini is created in the %windir% directory on the user's local computer and is used to store the corresponding security settings. These settings will apply to all users that may share the client computer for accessing embedded applications through a Web browser. Currently, the location for the webica.ini file cannot be changed.

If the user does not have sufficient permissions to write to this location (for example, if the user is on a restricted client PC), the file will simply not be created, and no error message will be displayed. In this situation, the user will continuously be prompted to select the appropriate client security each time that he accesses an embedded application.

The following is an example of a webica.ini file created after I have connected to a couple of different applications published on different servers through an ActiveX ICA client. For MS Word running on server 10.45.21.3, I selected Full Access and Never Ask Me Again; for PowerPoint running on 10.45.21.4, I selected Read Access and Never Ask Me Again.

[Access]
CurrentConnection=10.45.21.4
10.45.21.3=405
GlobalSecurityAccess=-1

10.45.21.4=404

As you can see, the file contains the appropriate references to the two servers, along with a numeric value corresponding to the access permissions that I selected. Table 3 lists the valid security attributes that can be used.

Table 3

Valid Security Attributes for the webica.ini File

Numeric Value

Access Level

–1

No security setting has been specified. Prompt the user for input.

403

No access.

404

Read access.

405

Full access.

In addition to any server IP addresses that may exist in the file, there are also two special entries:

  • CurrentConnection—This shows the IP address of the server that was most recently connected. It has no function with regard to setting access security.

  • GlobalSecurityAccess—This value determines the default behavior for all embedded sessions. The default value of –1 signals that the file security dialog should be displayed for all servers not already listed in the webica.ini file. If any other numeric security value is specified, it will automatically be used as the default access permissions, regardless of whether a specific server entry exists. So, for example, if it was GlobalSecurityAccess = 405, then all application connections would default to full access, even if a different security level existed for a particular server.

One final point to note is that file security permissions are handled on a per-server (IP address), not per-application, basis. In my example, this would mean that all published applications on the server 10.45.21.3 would default to full access, while those on 10.45.21.4 would default to read access. In both situations, no further prompting would be made to the user because the options have already been set.

Now you may be wondering what happens if an application is published across multiple servers. Will the user get prompted each time that he connects to the same published application running on a different server? The answer is yes. For example, if MS Word is published on 10.45.21.3 and on 10.45.21.11, then the permissions that I set when running MS Word on one server will not automatically apply when I run MS Word on the other.

If you are planning to push out a preconfigured webica.ini file to your users, make sure that all of the desired servers are listed within the file and that they are providing consistent security permissions. You do not want to get into a situation where access privileges are set differently for multiple servers that are publishing the same application.

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