Friday, December 5, 2014

Pitfalls running E11 as embedded SWT browser in Eclipse

Recently I implemented a preview view for an Xtext DSL that uses an embedded jetty and renders a JSF screen without deployment. To make bidirectional navigation possible from Xtext to JSF and the other way round, I decided to use websockets. That worked pretty well since I am working on a mac, but when the customer tried to used it the application did not work at all because of Windows and IE11.

First of all there is a bug that runs IE in compatibility mode to IE9 that does not have websockets integrated. :-( After switching to Luna 4.4.1 it worked until the next bomb exploded. After exactly 6 reloads the browser raised a Security Error when someone starts to establish a websocket connection... That is because IE11 and below do not really close a websocket implicitly when a page is reloaded or closed as it happens in "modern" browsers automatically. The number of connections that are allowed is hard coded deep inside the registry. BTW I hate that registry stuff sooooo much.... After closing the websockets explicitly everything works as expected even within Windows 8.1 and IE11. The whole story took me 2 full days ... Why the hell does Microsoft always do things different in their Internet Explorer. Luckily I do not have to work with that environment sooo often.


  1. Hi Holger!

    Yeah I know that this post is a little bit old, BUT maybe someone has the same problem:

    We had some sort of the same issue and your blog entry helped us to solve it.
    Our problem was that we tried to open more than 6 Websockets at the same time - and yeah thats not possible if it's not configured in the registry.

    First of all we tried to increase the number of connections with the group policy - yeah there is an entry for that but the embedded browser didn't care. There is only one possibility to increase the number - 1. find the registry key which will be used for the browser version of the embedded browser (KEY FEATURE_BROWSER_EMULATION) - 2. Create a new key (FEATURE_WEBSOCKET_MAXCONNECTIONSPERSERVER) and create a new DWORD (name: data: )

    More informations about controlling the embedded browser:
    Especially for the browsers websockets:

  2. How did you "explicitly" close the connection. Having this same issue.