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another way to access a cloud VM’s VNC console

February 8th, 2014 by

If you have used a cloud, that was based on OpenStack, you will have seen the dashboard including a web-based VNC access using noVNC + WebSockets.
However, it was not possible to access this VNC directly (e.g. with my favourite gvncviewer from the gtk-vnc-tools package), because the actual compute nodes are hidden and accessing them would circumvent authentication, too.

I want this for the option to add an OpenStack-backend to openQA, my OS-autotesting framework, which emulates a user by using a few primitives: grabbing screenshots and typing keys (can be done through VNC), powering up a machine(=nova boot), inserting/ejecting an installation medium (=nova volume-attach / volume-detach).

To allow for this, I wrote a small perl script, that translates a TCP-connection into a WebSocket-connection.
It is installed like this
git clone https://github.com/bmwiedemann/connectionproxy.git
sudo /sbin/OneClickInstallUI http://multiymp.zq1.de/perl-Protocol-WebSocket?base=http://download.opensuse.org/repositories/devel:languages:perl

and is used like this
nova get-vnc-console $YOURINSTANCE novnc
perl wsconnectionproxy.pl --port 5942 --to http://cloud.example.com:6080/vnc_auto.html?token=73a3e035-cc28-49b4-9013-a9692671788e
gvncviewer localhost:42

I hope this neat code will be useful for other people and tasks as well and wish you a lot of fun with it.

Some technical details:

  • The code is able to handle multiple connections in a single thread using select.
  • HTTPS is not supported in the code, but likely could be done with stunnel.
  • WebSocket-code was written in 3h.
  • noVNC tokens expire after a few minutes.

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