Skype for business screen sharing and file sending - incomplete

[CRDF18]

Hi

We are getting reports of our Skype for business screen sharing or file sending isnt working today. We have had all the rules setup for a long while with no reported issues but today its not working.

When i check the firewall logs for a particular user nothing is being blocked. What i can see that when he tries to share his screen according to the logs the action is allowed, his machine goes out to microsoft IP addresses, its not being decryted, its going to ports in the 50000 range (i believe this is the correct ports for S4B) but the application is coming up incomplete, which i think is the issue here. The end user just gets a message "couldnt connect to the presentation"

Our rules for Skype is split into two rules.

One with ms-lync, ms-lync-audio, ms-lync-base, ms-lync-content-sharing, ms-lync-online, ms-lync-online-apps-sharing, ms-lync-video, ms-office365-base, office365-consumer-access, office365-enterprise-access, RTCP, RTP, RTP-base, skype, skype-probe, ssl, stun, unknown-udp, web-browsing, web socket & windows-azure-base applications all with application-default services.

The other rule just for the Stun application and any service.

I have tried moving these rules up and beneath the web access rule but still no luck.

Is anyone else having this issue?

[OtakarKlier · Accepted solution]

Hello,

This could be on the 'other' side, meaning they may have changed something such as enabling Decryption or something else. Incomplete means that the tcp 3-way handshake did not complete, or it completed and nothing followed. 

Hope that helps.

[BPry]

@CRDF18,

@OtakarKlier  is right, I don't think that this is actually on your end at all. Something likely changed for the party you were attempting to connect to. 

[CRDF18]

Thanks we will go back to the 3rd party we were having issues with and get them to check out their firewall and also maybe try them from another connection