On a machine running VSM Agent

22: SSH daemon

Just as for the VSM server, there must be an SSH daemon running on all VSM agent machines. This daemon is normally listening to port 22, although it can listen to other ports as well. See the entry about port 22 at On a machine running VSM Server.

300: ThinLinc Web Access

By default, ThinLinc’s Web Access service tlwebaccess is available on TCP port 300. Traffic to this port is encrypted (TLS).

Note

The port on which tlwebaccess runs is configurable via the parameter /webaccess/listen_port. See Parameters in /webaccess/ for details.

904: VSM Agent

The VSM agent listens on port 904 for incoming requests from the VSM server host. The traffic is not encrypted, but the VSM agent only allows connections originating from a port lower than 1024, from a list of known IP addresses. The protocol in use is XMLRPC through HTTP.

1010: ThinLinc web administration interface (tlwebadm)

By default, ThinLinc’s web-based administration interface is available on TCP port 1010. See the entry about port 1010 at On a machine running VSM Server.

5901–5999: VNC servers for first 99 sessions

Ports 5901–5999 are used by Xvnc processes serving display numbers strictly below 100.

4900–5899: Tunnels to clients

The ports in this interval are used as server-side endpoints for the SSH tunnels used to access local resources of the client, for example local drives, serial ports and sound.

This interval is used for sessions with display number strictly below 100.

The algorithm used for calculating which ports to use for a specific display number in this interval is:

4900 + display-id × 10 + SERVICE_SLOT

where SERVICE_SLOT is a number defined under /vsm/tunnelservices.

6001–8000: X display ports

If Xvnc is configured to listen for incoming TCP requests from X Window System clients on other hosts, ports 6001–8000 are used by display numbers 1–2000. The default is not to listen for incoming TCP requests, so in the default configuration, the ports in this interval are not open.

Port 32767 downwards to 11857

The algorithm described below is used to allocate ports for the Xvnc process and for the server-side endpoints for SSH tunnels to access local resources of the client. This algorithm is used for sessions with display numbers strictly higher than 99.

Each session is allocated /vsm/tunnelslots_per_session (default value 10) + 1 ports, leading to an allocation of 11 ports per session with the default configuration. The ports are allocated starting with the port given as /vsmagent/max_session_port (default 32767), and then downwards. This means that the ports are aligned upwards as closely as possible to the upper limit defined. This is a good practice to avoid collisions with other services running on the machine.

Some examples follow

Display number 50

The VNC port will be 5950 which is:

5900 + display.

The tunnel ports allocated for this display are 5400–5409, which is:

4900 + (10 × display) + SERVICE_SLOT

where SERVICE_SLOT is 0–9.

Display number 100, /vsmagent/display_min = 10 (the default), /vsmagent/max_session_port = 32767.

The VNC port will be 32757, which is:

32767 - ((display - 100) × (/vsm/tunnelslots_per_session + 1) + /vsm/tunnelslots_per_session))

Ports 32758–32767 (inclusive) will be used for tunnel ports.

Display number 300, /vsmagent/display_min = 100, /vsmagent/max_session_port = 32767 (the default).

The VNC port will be 30557 which is:

32767 - ((display - 100) × (/vsm/tunnelslots_per_session + 1) + /vsm/tunnelslots_per_session))

Ports 30558–30567 (inclusive) will be used for tunnel ports.

Display number 600, /vsmagent/display_min = 300, /vsmagent/max_session_port = 32767 (the default).

The VNC port will be 29457, which is:

32767 - ((display - 300) × (/vsm/tunnelslots_per_session + 1) + /vsm/tunnelslots_per_session))

Ports 29458–29467 (inclusive) will be used for tunnel ports.