Virtual channels for VNC?

Question

Does anybody know weather VNC (RFB) supports virtual channels and add-ins to them like it is in the RDP (Microsoft Terminal Services)? I just want to transfer my own data across a VNC connection...

Answer 1

VNC/RFB does not have virtual channels unfortunately.

Here is the best reference I've found to the RFB protocol: http://tigervnc.org/cgi-bin/rfbproto

Without knowing more about what you are trying to send and which direction(s), there are a few of options that come to mind:

• The tight encoding has file-transfer support. There is a poorly formatted specification for the full tight encoding here: http://vnc-tight.svn.sourceforge.net/viewvc/vnc-tight/trunk/doc/rfbtight.odt?revision=3619

• If you have control of both client and server, then you could define a custom encoding that allows you to send your data. The client would advertise that it supports the encoding and if the server supports it then it will start using it.

• You could use the clipboard messages (ClientCutText and ServerCutText) and if you need to send binary data that create a custom encoding the data as ISO 8859-1 (Latin-1). The downside is that if the server doesn't support it and the client sends the data it will get pasted to the server.

• If you just need to send from the server to the client, then you could use a framebufferUpdate message that sends data outside the current viewport (i.e. 123 pixels beyond the right side of the viewport). Clients without support may not handle this well though.

• Another option if you just need to send from the server to the client, is that you could send a framebufferUpdate within the viewport with a special marker and then immediately send a framebufferUpdate (even in the same packet) with the real visible data to replace it. This would work with existing clients (a bit more overhead). Clients might see brief flicker though.