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File Transfer Call Flow/Modality ? RRS feed

  • Question

  • We are having problems with File Transfers when 3 or more people are in a SFB chat on our VPN network.  We receive the error "We can't connect to the server for sharing right now" and "Network issues are keeping you from sharing powerpoint slides, whiteboard, etc"

    - SFB 2019 on Windows Server 2019 fully up to date.  1xFE, 1xEdge, 1xRP
    - All file transfers work fine internally and externally (external network, no VPN).  
    - A peer-to-peer file transfer between 2 clients on VPN zone also works fine.  As soon as a 3rd person is added to the chat, file transfers fail
    - Audio/Video calls work fine

    My question is what can I do from a Skype perspective to troubleshoot this?  What is the expected call flow/modality for a file transfer?

    I have looked through the firewall and see TCP 443 from client to FE server when sharing a file with 3 or more people.  This is what I expect (MCU modality?) but I still get errors in Skype. In Snooper I can see log entries where the at the time that I'm sending files but I can't identify any errors.





    • Edited by GregKops Tuesday, May 5, 2020 7:03 PM
    Tuesday, May 5, 2020 6:59 PM

All replies

  • Hi GregKops

    According to your description, can we understand that this issue is only happening in VPN network?

    In this case, it recommends you first check this guidance to see if it can troubleshoot your issue.

    Also you can try to run the command “Get-CsConferencingCinfiguration” to make sure each of port range for client traffic type is unique. For example, you might configure the port ranges like this:


    To my knowledge, the most common file transfer method is through Instant Message(or “P2P File Transfer”).The following picture can be used to quickly reference which types of modalities support which of the two communication models.


    Besides, please check if there is any related error message in Front end server event viewer. 

    Best Regards,
    Jimmy Yang

    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.
    Wednesday, May 6, 2020 3:20 AM
  • Hi,
    Is there any update on this case?
    Please feel free to drop us a note if there is any update.
    Have a nice day!

    Best Regards,
    Jimmy Yang


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com

    Sunday, May 17, 2020 3:52 PM