I have a named sql instance on SQL 2012. The issue is that the clients is having problem connecting to it when the firewall is on, this is not consistent. The connection is fine when I disabled the firewall. When I turned the Windows firewall back on, it will work for awhile and it fails. I checked the SQL configuration manager and saw that a dynamic port is assigned to the named instance. I did put that in the firewall rule and unblock it. I also put TCP 1433 and 1434 as well as the browser service port, TCP\UDP 2382 and it still didn't work.
What is the best way to determine what port does the named instance are listening?
Thanks