Unable to reach the Defender Security Server (DSS). The "Test" option from Desktop Login does not work, it states that the Defender Security Server is unavailable.
In the DSS log, the message, "Failed to bind to IP Address: (Port number)" or "Failed to bind Port: (Port number)" appears.
This can be caused by the requested port being in use on the system where the DSS in running.
To check if the port is in use, from the command line type netstat -an.
The output may be very long so you can export it to a file to make it searchable, e.g. netstat -an > c:\netstat.txt
The port is a UDP port, i.e., 1645 or 1812 (as defined on your Access Node).
If the port(s) are in use, try a different port on the Access Node or stop the program that the port is currently being used by. Once that has been done restart the Defender Security Server (DSS) service. You can confirm in the DSS log if there is still a bind issue (logs are located here: C:\Program Files\Quest Software\Defender\DSS Active Directory Edition\Logs, on the DSS server).
If the port is not in use restart the DSS service and confirm if it can now bind to the required port. Alternately, install the DSS on another server. For example, there may be port binding issues on a Domain Controller, if that's where the DSS is currently installed.
For more information on Access Node configuration, please see Knowledge Article 45588, Defender Access Node Configuration.
Below is an example from netstat -ab showing the output, when a Access Node using port 1812 is assigned to the DSS
UDP defsvr:1812 *:* 3400