#1490 Connection gracefully closed

[Woody Smith]

TightVNC server running on
Windows 10 build 1903 and 1909, 64bit
8GB ram
Dell 3010, mini tower
using motherboard video (Intel chip)

TightVNC client running on
Windows 10 build 1903 and 1909, 32bit
4GB ram
DELL Latitude 13, laptop

OpenShell
downloaded from
https://github.com/PowerShell/Win32-OpenSSH/wiki/Install-Win32-OpenSSH
version v8.0.0.0p1-Beta
same version on both computers

TightVNC 2.8.27
same version on both computers

Both computers are on a local lan in the same room.
Both computers have been screened for malware and drives have been defraged.
Both computers firewalls are turned off.
Both computers antivirus has been turned off.

Installed OpenSSH. Success running ssh.exe in CMD to open a SHH Tunnel.
Using port 501xx
Login is by authentication keys, not passwords

I have TightVNC server running on port 65xx. I have tried port 5900.

When I run TightVNC client directly to the TightVNC Server, it works.

When I run TightVNC Viewer though the SSH Tunnel I get the immediate message
"The connection has been gracefully closed."
I recognize this means the server closed the connection.

I have searched the Internet and do not find how to activate verbose output for debugging.
I have searched the Windows Event Logs, but no help.
I have found the TightVNC Server logs at
%userprofile%\AppData\Roaming\TightVNC
but the logs did not reveal anything.
The server computer is logged in and at the Windows Desktop
The client computer is logged in and at the Windows desktop
I used PUTTY instead of SSL command line to open the SSH Tunnel. Same error from TightVNC client.

[Woody Smith]

Forgot to add. I am using port forwarding in the SSH command like this
ssh -L 127.0.01:501xx:192.168..1.xxx:501xx name@192.168.1.xxx -P 65xx

[Woody Smith]

Today captured SSH debug log after TightVNC tries to connect. I changed port to see if that would make a difference.

excalibremanage\station02@STATION-02 C:\Users\station02.DOMAN-NAME-REMOVED>debug1: Connection to port 40200 forwarding to IP-ADDRESS-REMOVED port 40200 requested.
debug2: fd 8 setting TCP_NODELAY
debug2: fd 8 setting O_NONBLOCK
debug3: fd 8 is O_NONBLOCK
debug1: channel 2: new [direct-tcpip]
debug3: send packet: type 90
debug3: receive packet: type 91
debug2: channel 2: open confirm rwindow 2097152 rmax 32768
debug3: receive packet: type 96
debug2: channel 2: rcvd eof
debug2: channel 2: output open -> drain
debug2: channel 2: obuf empty
debug2: channel 2: chan_shutdown_write (i0 o1 sock 8 wfd 8 efd -1 [closed])
debug2: channel 2: output drain -> closed

TightVNC Error dialog box appears at this point.
DialogBox Title=localhost:40200 TightVNC Viewer
DialogBox MSG='Connection has been gracefully closed.'
After closing dialog box SSH debug throws messages below.

debug2: channel 2: read<=0 rfd 8 len 0
debug2: channel 2: read failed
debug2: channel 2: chan_shutdown_read (i0 o3 sock 8 wfd 8 efd -1 [closed])
debug2: channel 2: input open -> drain
debug2: channel 2: ibuf empty
debug2: channel 2: send eof
debug3: send packet: type 96
debug2: channel 2: input drain -> closed
debug2: channel 2: send close
debug3: send packet: type 97
debug3: channel 2: will not send data after close
debug3: receive packet: type 97
debug2: channel 2: rcvd close
debug3: channel 2: will not send data after close
debug2: channel 2: is dead
debug2: channel 2: garbage collecting
debug1: channel 2: free: direct-tcpip: listening port 40200 for IP_Address_Removed port 40200, connect from 127.0.0.1 port 51388 to 127.0.0.1 port 40200, nchannels 3
debug3: channel 2: status: The following connections are open:
#1 client-session (t4 r0 i0/0 o0/0 e[write]/0 fd 5/6/7 sock -1 cc -1)
#2 direct-tcpip: listening port 40200 for IP_Address_Removed port 40200, connect from 127.0.0.1 port 51388 to 127.0.0.1 port 40200 (t4 r1 i3/0 o3/0 e[closed]/0 fd 8/8/-1 sock 8 cc -1)

[Woody Smith]

Ran some isolation tests. Same client computer. Same server computer. Port 22 for SSH. Port 5900 for TightVNC. Only difference is server computer logged into Windows SBS 2011 domain - SSH tunnel works, TightVNC fails. Server logged in as local account - SSH tunnel works, TightVNC works. Issue seems to be sockets.
Attaching client and server logs for both domain test and local test. ssh_config and sshd_config identical for both domain test and local test. The TightVNC log files where empty both tests.

[Woody Smith]

Forgot to add this. TightVNC control of OpenSSH server computer WITHOUT SSH works. Fails with SSH tunnel.