Find-DbaInstance - Fix TcpConnected false for multiple named instances; add verbose messages

The TcpClient in Test-TcpPort was created once (in begin{}) and shared
across all port tests. After the first successful Connect()+Close(), the
client was disposed, causing all subsequent port tests to throw
ObjectDisposedException (caught, returning IsOpen=False).

Fix: create a new TcpClient per port test (moved to process{}) with
Dispose() in a finally block.

Also filter out port 0 from Browser results - DbaBrowserReply.TCPPort
defaults to 0 for instances that don't report a TCP port, and testing
port 0 can leave the socket in an error state.

Added Verbose messages throughout the Browser scan path to aid
debugging: Browser results, port test results, per-instance BrowseReply
TCPPort lookup and outcome.

Co-authored-by: Andreas Jordan <andreasjordan@users.noreply.github.com>

Author: github-actions[bot]

public/Find-DbaInstance.ps1

@@ -350,16 +350,22 @@ function Find-DbaInstance {
                         try {
                             Write-ProgressHelper -Activity "Processing: $($computer)" -StepNumber ($stepCounter++) -Message "Probing Browser service"
                             $browseResult = Get-SQLInstanceBrowserUDP -ComputerName $computer -EnableException
-                            $ports = $browseResult.TCPPort | Test-TcpPort -ComputerName $computer
+                            Write-Message -Level Verbose -Message "Browser returned $($browseResult.Count) instance(s): $(($browseResult | ForEach-Object { "$($_.InstanceName):$($_.TCPPort)" }) -join ', ')" -Target $computer -FunctionName Find-DbaInstance
+                            # Filter port 0 - Browser returns 0 for instances that don't report a TCP port (default instances)
+                            $ports = $browseResult.TCPPort | Where-Object { $_ -gt 0 } | Test-TcpPort -ComputerName $computer
+                            Write-Message -Level Verbose -Message "Port test results from Browser: $(($ports | ForEach-Object { "Port $($_.Port)=$($_.IsOpen)" }) -join ', ')" -Target $computer -FunctionName Find-DbaInstance
                         } catch {
+                            Write-Message -Level Verbose -Message "Browser scan failed: $_" -Target $computer -FunctionName Find-DbaInstance
                             # here to avoid an empty catch
                             $null = 1
                         }
                         # Fall back to default port testing if Browser returned no port info
                         # (e.g. SQL Server 2022+ where Browser is deprecated, or default instances
                         # which don't report a TCP port via Browser UDP)
                         if (-not $ports) {
+                            Write-Message -Level Verbose -Message "No port info from Browser, falling back to default ports: $($TCPPort -join ', ')" -Target $computer -FunctionName Find-DbaInstance
                             $ports = $TCPPort | Test-TcpPort -ComputerName $computer
+                            Write-Message -Level Verbose -Message "Fallback port test results: $(($ports | ForEach-Object { "Port $($_.Port)=$($_.IsOpen)" }) -join ', ')" -Target $computer -FunctionName Find-DbaInstance
                         }
                     } else {
                         $ports = $TCPPort | Test-TcpPort -ComputerName $computer
@@ -455,16 +461,20 @@ function Find-DbaInstance {
                             $object.Confidence = 'Medium'
                             if ($object.BrowseReply.TCPPort) {
                                 $object.Port = $object.BrowseReply.TCPPort
+                                Write-Message -Level Verbose -Message "Instance $instance: Browser reported TCPPort $($object.Port), checking PortsScanned: $(($object.PortsScanned | ForEach-Object { "Port $($_.Port)=$($_.IsOpen)" }) -join ', ')" -Target $computer -FunctionName Find-DbaInstance
 
                                 $object.PortsScanned | Where-Object Port -EQ $object.Port | ForEach-Object {
                                     $object.TcpConnected = $_.IsOpen
+                                    Write-Message -Level Verbose -Message "Instance $instance: Port $($_.Port) IsOpen=$($_.IsOpen), TcpConnected set to $($object.TcpConnected)" -Target $computer -FunctionName Find-DbaInstance
                                 }
                             } else {
                                 # Default instance - Browser doesn't report a specific TCP port,
                                 # check if any of the fallback ports we tested is open
+                                Write-Message -Level Verbose -Message "Instance $instance: Browser has no TCPPort (default instance), checking PortsScanned for any open port: $(($object.PortsScanned | ForEach-Object { "Port $($_.Port)=$($_.IsOpen)" }) -join ', ')" -Target $computer -FunctionName Find-DbaInstance
                                 $object.PortsScanned | Where-Object IsOpen | Select-Object -First 1 | ForEach-Object {
                                     $object.Port = $_.Port
                                     $object.TcpConnected = $true
+                                    Write-Message -Level Verbose -Message "Instance $instance: Found open port $($_.Port), TcpConnected set to True" -Target $computer -FunctionName Find-DbaInstance
                                 }
                             }
                         }
@@ -814,21 +824,20 @@ function Find-DbaInstance {
                 [Parameter(ValueFromPipeline)][int[]]$Port
             )
 
-            begin {
-                $client = New-Object Net.Sockets.TcpClient
-            }
             process {
                 foreach ($item in $Port) {
+                    $client = New-Object Net.Sockets.TcpClient
                     try {
                         $client.Connect($ComputerName.ComputerName, $item)
                         if ($client.Connected) {
-                            $client.Close()
                             New-Object -TypeName Dataplat.Dbatools.Discovery.DbaPortReport -ArgumentList $ComputerName.ComputerName, $item, $true
                         } else {
                             New-Object -TypeName Dataplat.Dbatools.Discovery.DbaPortReport -ArgumentList $ComputerName.ComputerName, $item, $false
                         }
                     } catch {
                         New-Object -TypeName Dataplat.Dbatools.Discovery.DbaPortReport -ArgumentList $ComputerName.ComputerName, $item, $false
+                    } finally {
+                        $client.Dispose()
                     }
                 }
             }