System architecture of Skype presence in SharePoint

Business end-users really appreciate the SharePoint capability that displays presence information of your colleagues, e.g. in a people results overview. They take this capability for granted, and request the same in other (web)applications, and even on other devices - mobile in particular. However, that is not that trivial to accomplish. The SharePoint presence capability current really shines in the combinations of Microsoft specific clients - IE browser, Outlook mailclient -, and the Skype client process on the local device. That local Skype client process functions actually as interface gateway to access Skype functionalities: retrieve presence information, start chatting.

Windows OS
Presence indication in SharePoint pages works via Microsoft proprietary combination: IE plug-in, that communicates via a proprietary protocol on Windows OS level against the local Skype client (process). The local Skype client on its turn connects to the central Lync / Skype server.

With this IE plug-in enabled, and local Skype client active + logged in; the presence information of colleagues can be retrieved and visualized in IE

Mobile OS
On Mobile OS, the system architecture is in essence the same: the local Skype Client operates as ‘gateway’/interface to the central Skype server. Element of the local Skype client deployment is an API via which custom applications can invoke Skype (client) functionaliteit: Skype for Business App SDK. Current this API includes capabilities to start a chat, start a video playing. There is yet no endpoint in the Skype client API to retrieve presence information.

How-to have IE11 pick up local PAC file

In our company we utilize a cloud-hosted Proxy Automatic Configuration script (PAC file). On occasion it is convenient to switch to a local version, e.g. to investigate or troubleshoot. When we still were at IE9 this was easy, but since we’ve upgraded the company browser to IE11 it becomes more difficult. To promote interoperability across network stacks, Microsoft deprecated the option for a local PAC file. You can still configure it in Internet Settings, but IE 11 will simple ignore a local proxy auto-config file.

However, Microsoft also understands it’s backwards compatible responsibility. And therefore build in support to overrule the deprecation of local PAC file. The approach consists of 2 steps:

• Step 1: [source: Understanding Web Proxy Configuration] Via registry value 'HKLM\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\EnableLegacyAutoProxyFeatures' specify that it is ok to utilize the legacy Internet Settings. Note that in our company the regular users are not enabled to set this, as they are not administrator on their workstation. But the occasional usage of local proxy file is then also not for these regular end-users.
• Step 2: [source: local proxy which is set in the proxy auto config of IE11 is not processed correctly by IE11] Create the local PAC file as "c:/windows/system32/drivers/etc/proxy", and specify in IE as setting for automatic configuratio script = 'file://c:/windows/system32/drivers/etc/proxy'