disconnection by winVNC server immediately after succesfull authentication

Craig Hellon craig.hellon "at" avt.co.uk
Tue Mar 2 22:27:00 2004

I have a very odd issue with both realVNC and tightVNC. I have been succesfully tunnelling into my work PC from home for some time across the internet.  I then
decided to tryout tightVNC to see if the compression gives any significant performance benefit.  After installing this, (which maybe coincidence here, I dont know), I have been unable to establish a VNC session.  I have tried all four combinations or real and tight VNC,  client and server.  All of which fail.
I have run snoops at the server end and this is what I see:
server sends RFB 003.003
client sends RFB 003.003
server sends 4 bytes indicating security model "0002" (VNC authentication mode)
server sends 16byte challenge
client sends 16byte response (challenge DES encrypted with password).
server sends 4 byte response "0000" indicating authentication pass.
client sends 1 byte  "0"  indicating do not share desktop (I think)
server sends FIN
followed by client FIN
I cannot understand what is going wrong, ie why the VNC server decides to terminate the connection mid way through the handshake after a successful authentication.  Nothing has changed other than me installing tightVNC as well as the already installed realVNC.   I can connect fine across the LAN using any of the four combinations of tightVNC and realVNC server/client.  Am I suffering from a synchronisation issue here that only occurs when connecting from more remote locations.
I have switched on logging at the server but cannot view the logs until later this week.
Any useful advice would be gratefully received.