Step 1: Check whether the named instance is using a static or dynamic TCP port

1. Open SQL Server Configuration Manager.

2. Navigate to
   SQL Server Network Configuration → Protocols for [Instance Name].

3. Right-click TCP/IP and select Properties.

4. Go to the IP Addresses tab and review the IPAll section.

Static Port Configuration

• TCP Port: Contains a specific port number (for example, 1433 or another fixed port).

• TCP Dynamic Ports: Must be empty.

This confirms the SQL Server instance is using a static TCP port.

Dynamic Port Configuration

• TCP Port: Is empty.

• TCP Dynamic Ports: Contains 0.

When set to 0, SQL Server dynamically assigns an available TCP port at startup.
The actual assigned port can be found in the SQL Server error log or in SQL Server Configuration Manager after a restart.

⚠️ Note: If a value is entered under TCP Dynamic Ports, SQL Server may still change the port on restart. For predictable connectivity, always configure a static port under TCP Port.

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Step 2: If the named instance is using a dynamic port

1. While adding the MSSQL monitor, enable “Connect using Named Instance” and provide the instance name. For existing monitors, Edit and update the monitor to use instance name.

2. Ensure that the SQL Server Browser service is running on the SQL Server host.

SQL Server Browser and UDP Port Requirement

• Named instances using dynamic ports rely on the SQL Server Browser service to resolve the instance name to the correct TCP port.

• By default, SQL Server Browser listens on UDP port 1434, but this port can be changed based on customer configuration.

• The configured UDP port used by SQL Server Browser must be reachable between the monitoring server and the SQL Server host.

Verify UDP Connectivity

• Confirm which UDP port SQL Server Browser is listening on.

• Ensure that this UDP port is:

  • Open on the SQL Server host firewall

  • Allowed through any intermediate network firewalls

If the required UDP port is blocked or the SQL Server Browser service is not running, you may encounter the following error:

java.sql.SQLException: Unable to get information from SQL Server

This error indicates that the JDBC driver was unable to retrieve the TCP port information for the named instance.

Important Note (SQL Server 2005)

On SQL Server 2005, instance name resolution is handled exclusively by the SQL Server Browser service.
By default, the SQL Server Browser service is disabled and not configured to start automatically, so it must be manually enabled and started.

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Step 3: If the named instance is using a static port

• When a static TCP port is configured:

  • You can connect directly using the TCP port number instead of the instance name.

  • The SQL Server Browser service is not required.

  • No UDP ports are required for instance resolution.

• Configure the MSSQL monitor using:

  • Hostname/IP + Port number

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Alert: Common Causes of Connection Issues

• TCP/IP protocol is disabled for the SQL Server instance.

• The SQL Server service is not listening on the expected TCP port.

• Firewall rules block:

  • The configured TCP port (static port), or

  • The UDP port used by SQL Server Browser (dynamic port configuration).

• Incorrect usage of instance name or port number during monitor configuration.