Firewall

Each session will use its own port, so you must ensure that your firewall is not blocking access to these ports.
On *nix, you can use SSH tunnelling to workaround this.

Finding out what is happening

To enable session debugging, you must ensure that your server configuration does not delete the session files when the sessions terminate as it does by default.
Either modify the delete_session_files option and set it to False or you can just start the server from the command line with the following options:

winswitch_server --debug-mode --no-delete-session-files

The session directory is found in .winswitch/server/sessions/, each session will create a folder named after the session's display name. This directory will contain log files, icons, password files, etc. The log file should point you in the right direction, if not ask us
When the server starts a new session, it will log a message similar to this one:

NXServerUtil.start_daemon(Session(:84 - nx... logging to $HOME/.winswitch/server/sessions/84/nx.log

Locate this message and have a look at the session directory and its log file.

Session Types Options

On a client with all the required utilities installed, connecting to a server which is also fully configured, you should get the option of starting applications with any protocol that you like (NX, Xpra, VNC, SSH...).
The applet will only show you the options that are accepted by both ends, if one is missing that means that either the client or server is missing the required tool.

• For the applet, go to the Protocols tab of the Configuration screen and ensure that all the protocols are enabled.

  You may have to enable Advanced Mode in the General tab to be able to specify the location of applications that were not detected automatically

• For the server, you must open the Server Configuration and verify that the commands used (ie: xpra_command, nxagent_command...) are set and valid

For a comparison of the different session types, see here
Limitations:

• Microsoft Windows and Mac OSX cannot be used as servers for NX or Xpra sessions (SSH is only supported on Mac OSX)
• Microsoft Windows and Mac OSX can shadow an existing display using VNC, but only once
• RDP can only be served from a Microsoft Windows system

(Most of these limitations are dictated by the operating system itself, not by any design decisions of ours)