Clipboard limitations for file transfer in VNC sessions
I would like to understand the clipboard behavior differences between RDP and VNC in Remote Desktop Manager.
With RDP, I can copy and paste both text and files from my local machine to the remote system. In VNC sessions, clipboard redirection works only for text, while file copy-paste is not supported.
I am aware that file transfers can be done through the VNC file-transfer utility provided by some VNC servers, but I would like more information specifically about clipboard-based file copy-paste. This method is much faster and more convenient, so I would like to know whether the limitation is due to the VNC protocol, the implementation used by RDM, or specific server-side settings.
Any clarification on whether clipboard file transfer can be enabled or improved in VNC sessions would be appreciated.
Thank you.
All Comments (6)
Hello
Currently we don't support file transfer by copy-paste in embedded VNC sessions.
As you've suggested, this is essentially a server-defined feature. The VNC (RFB) specification defines an extended clipboard protocol that theoretically supports file transfer, but in effect the file transfer parts of the spec are undefined and, as far as I know, not implemented by any server. If there's a server you're using that supports this (likely in companion with their own VNC client) please let me know and we can look into adding support on our side. I'm not aware of a VNC server that _does_ support this, maybe RealVNC?
Thanks and kind regards,
Richard Markievicz
Thank you for your reply.
Regarding RealVNC, I read:
"It can be enabled or disabled using the ClipboardFT parameter in RealVNC Server. File transfer via copy and paste is currently only available when both RealVNC Viewer and RealVNC Server are running on Windows.
Source: https://help.realvnc.com/hc/en-us/articles/360002250477-Transferring-Files-Between-Computers#using-file-manager-0-1"
In my case, UltraVNC Server is installed on the machine I connect to, and I use RDM on the machine I use to connect.
Thanks!
Hello
For RealVNC, it's a special case because their implementation is proprietary (closed source and specification). It's not something we can implement unless they make their implementation public (which is extremely unlikely) or without a significant effort to reverse engineer their protocol (which is technically feasible, but so challenging it's unlikely to happen). To get this feature with RealVNC and RDM, the only option is to use RealVNC viewer in "External" mode unfortunately.
For UltraVNC, file transfer is supported (and should be available in RDM via the toolbar) but it's done through a specific file transfer interface. To my knowledge, UltraVNC does not support transferring files via the clipboard. If that's something that they've recently added or are adding in the future, we can look at integrating it on our side (their protocol implementations are public / open source).
Sadly this is a result of the fragmentation of the VNC (RFB) protocol. Modern features like this that are not defined by the core protocol are implemented using vendor specific extensions. Only if those extensions are open and interoperable can we implement them.
Please, let me know if something isn't clear or you have other questions
Kind regards
Richard Markievicz
Thank you for your comprehensive reply, everything is clear now! Since we connect to machines with UltraVNC servers in my company, from what I understand, copying and pasting files is impossible. We can close the ticket, thank you very much!
Hello
One thing I can suggest if this is important to you, is requesting the feature from UltraVNC. Maybe that's something they're interested in adding.
Thanks and kind regards,
Richard Markievicz
Issue opened. Thanks!
https://github.com/ultravnc/UltraVNC/issues/322