During https://support.zabbix.com/browse/ZBX-21510 NodeAdress tests, we found that the error message 'Connection to Zabbix server "localhost" refused' contains an outdated list of possible reasons that we should actualize and update.

Steps to reproduce:

• Enable 'High availability cluster parameters' in etc/zabbix_server.conf:

  ####### High availability cluster parameters #######
  
  ## Option: HANodeName
  #	The high availability cluster node name.
  #	When empty, server is working in standalone mode; a node with empty name is registered with address for the frontend to connect to.
  #
  # Mandatory: no
  # Default: 
  HANodeName=zabbix-node-01
  
  ## Option: NodeAddress
  #	IP or hostname with optional port to specify how frontend should connect to the server.
  #	Format: <address>[:port]
  #
  #	This option can be overridden by address specified in frontend configuration.
  #
  # Mandatory: no
  # Default: 
  NodeAddress=localhost:10055
  

• Run zabbix server
• Check Reports->System information page

Result: Error message appears:

Connection to Zabbix server "localhost" refused. Possible reasons:
1. Incorrect server IP/DNS in the "zabbix.conf.php";
2. Security environment (for example, SELinux) is blocking the connection;
3. Zabbix server daemon not running;
4. Firewall is blocking TCP connection.
Connection refused

Expected:

• According to the documentation https://www.zabbix.com/documentation/current/en/manual/concepts/server/ha#:~:text=Make%20sure%20that%20Zabbix%20server%20address%3Aport%20is%20not%20defined Zabbix server address:port shouldn't be defined so the first point from the list ' Incorrect server IP/DNS in the "zabbix.conf.php";' should be actualized and updated.
• As the second point need to add information that NodeAddress should contain an empty port or the port should be equal ListenPort param value
• Other points from the list should stay the same