Johny Skovdal Johny Skovdal - 1 month ago 6
C# Question

How to navigate from browser to application in Citrix

I am currently developing an integration between a web app and a windows application, where everything works fine on standard setups. However, introducing Citrix to the equation complicates everything quite a bit.

The current solution



At the moment we have a POC (proof of concept) running with custom Uri Scheme registration to a little exe we have developed, and listing active instances with Global Atom (using this trick to list search all entries). This way, we can see if an instance of our application is running. If it is, we call it via SendMessage, and if not, we start the application in a new process, and wait for it to be ready, for us to call it.

The issues introduced with Citrix



Now, when using Citrix Desktop Sessions, we do not suspect we will run into any issues, but with Application Sessions (AKA XenApp) the Citrix documentation states: "URL redirection works only for desktop sessions, not application sessions.", and we have therefor run into a brick wall with our implementation. So to sum up, we now have issues with accomplishing the following steps:


  1. Registering a custom URI Scheme handler: That might not at all be supported. The way we use it now, it points to an application on disk, but the Application is installed on a server.

  2. Detecting if an instance is running: We do not know if Global Atoms are even possible in this setup, and I have been unable to find any documentation on this.

  3. Calling a XenApp window with SendMessage: When running the simplest XenApp configuration we could reproduce, we can inspect the hosting process and get the handle to our application, but the application never gets the message sent at it.



Solving it within the current solution scope



Can the above scenario be accomplished in a Citrix environment using Application Sessions? If so, how? The tests I have performed so far, appears to confirm my suspicions that it is simply not supported within this setup.

Solving it in similar fassion



The POC we have developed is simple and modular, and changing how instances are located and communicated with is easily implemented and made configureable to our clients specific setup. It will then require other ways of detecting, launching and communiting with the primary application.


  1. Just detecting a running application has proven difficult (another question hat has not yet been answered), and the Global Atoms approach does not seem to work.

  2. Launching the app if it is not running, is something I have pretty much given up on, given how many different ways the app can be distributed in such a setup, so it will probably have to be a requirement that the application is already running.

  3. Even though I can retrieve what the handle is for the mainwindow, I am not able to use SendMessage either in a Citrix setup. It simply does not process the message I am sending at it. Is that also something XenApp does not support? I could not find find any documentation on this. Alternative ideas to call into the hosted application are very welcome.


Answer

In the end the solution(s) was extremely simple for our citrix customers, as they could either:

  1. Open our software first, launch a browser window from within (we have various links that opens browsers), and navigation now works flawlessly.
  2. Customize a hosted browser application, to run in the same server environment as our software, and then our POC was able to launch our software as though it was a regular desktop environment.