Align SqlException Numbers across platforms

Author: David-Engel

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ManagedSni/SniError.netcore.cs

@@ -5,6 +5,8 @@
 #if NET
 
 using System;
+using System.ComponentModel;
+using System.Net.Sockets;
 
 namespace Microsoft.Data.SqlClient.ManagedSni
 {
@@ -40,7 +42,23 @@ public SniError(SniProviders provider, uint sniErrorCode, Exception sniException
             lineNumber = 0;
             function = string.Empty;
             this.provider = provider;
-            nativeError = nativeErrorCode;
+            if (nativeErrorCode == 0)
+            {
+                nativeError = nativeErrorCode;
+                if (sniException is SocketException socketException)
+                {
+                    // SocketErrorCode values are cross-plat consistent in .NET (matching native Windows error codes)
+                    nativeError = (uint)socketException.SocketErrorCode;
+                }
+                else if (sniException is Win32Exception win32Exception)
+                {
+                    nativeError = (uint)win32Exception.NativeErrorCode; // Replicates native SNI behavior
+                }
+            }
+            else
+            {
+                nativeError = nativeErrorCode;
+            }
             sniError = sniErrorCode;
             errorMessage = string.Empty;
             exception = sniException;

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ManagedSni/SniTcpHandle.netcore.cs

@@ -375,6 +375,8 @@ private static Socket Connect(string serverName, int port, TimeoutTimer timeout,
 
                 IEnumerable<IPAddress> ipAddresses = GetHostAddressesSortedByPreference(serverName, ipPreference);
 
+                SocketException lastSocketException = null;
+
                 foreach (IPAddress ipAddress in ipAddresses)
                 {
                     bool isSocketSelected = false;
@@ -426,7 +428,7 @@ private static Socket Connect(string serverName, int port, TimeoutTimer timeout,
                             {
                                 if (timeout.IsExpired)
                                 {
-                                    return null;
+                                    throw new Win32Exception(258, "The operation has timed out.");
                                 }
 
                                 int socketSelectTimeout =
@@ -471,6 +473,7 @@ private static Socket Connect(string serverName, int port, TimeoutTimer timeout,
                         SqlClientEventSource.Log.TryAdvancedTraceEvent(
                             "{0}.{1}{2}THIS EXCEPTION IS BEING SWALLOWED: {3}",
                             nameof(SniTcpHandle), nameof(Connect), EventType.ERR, e);
+                        lastSocketException = e;
                     }
                     finally
                     {
@@ -479,6 +482,14 @@ private static Socket Connect(string serverName, int port, TimeoutTimer timeout,
                     }
                 }
 
+                if (lastSocketException != null)
+                {
+                    SqlClientEventSource.Log.TryAdvancedTraceEvent(
+                        "{0}.{1}{2}Last Socket Exception: {3}",
+                        nameof(SniTcpHandle), nameof(Connect), EventType.ERR, lastSocketException);
+                    throw lastSocketException;
+                }
+
                 return null;
             }
         }
@@ -588,6 +599,7 @@ private static Socket ParallelConnect(IPAddress[] serverAddresses, int port, Tim
                     {
                         SqlClientEventSource.Log.TryAdvancedTraceEvent(
                             "{0}.{1}{2}ParallelConnect timeout expired.", nameof(SniTcpHandle), nameof(ParallelConnect), EventType.INFO);
+                        // We will throw below after cleanup
                         break;
                     }
 
@@ -654,6 +666,11 @@ private static Socket ParallelConnect(IPAddress[] serverAddresses, int port, Tim
 
                 if (connectedSocket == null)
                 {
+                    if (timeout.IsExpired)
+                    {
+                        throw new Win32Exception(258, "The operation has timed out.");
+                    }
+
                     SqlClientEventSource.Log.TryAdvancedTraceEvent(
                         "{0}.{1}{2}No socket connections succeeded. Last error: {3}",
                         nameof(SniTcpHandle), nameof(ParallelConnect), EventType.ERR, lastError);