ipv4 prioritization added

Author: HaikAsatryan

src/Communicator/Communicator.csproj

@@ -8,7 +8,7 @@
         <PackageReadmeFile>Readme.md</PackageReadmeFile>
         <Authors>Pandatech</Authors>
         <Copyright>MIT</Copyright>
-        <Version>2.2.0</Version>
+        <Version>2.2.1</Version>
         <PackageId>Pandatech.Communicator</PackageId>
         <Title>SMS and Email Communication helper</Title>
         <PackageTags>pandatech;communicator;messaging;email;smtp;mailkit;mimekit;sms;twilio;dexatel;notifications;transactional;dotnet;net9;minimal-api;dependency-injection</PackageTags>

src/Communicator/Services/Implementations/EmailService.cs

@@ -1,4 +1,6 @@
-using Communicator.Helpers;
+using System.Net;
+using System.Net.Sockets;
+using Communicator.Helpers;
 using Communicator.Models;
 using Communicator.Options;
 using Communicator.Services.Interfaces;
@@ -77,13 +79,69 @@ private static SmtpClient CreateClient(EmailConfiguration config)
 
    private static async Task ConnectAndAuthAsync(SmtpClient client, EmailConfiguration config, CancellationToken ct)
    {
-      var socketOptions = ResolveSocketOptions(config.SmtpPort);
-      await client.ConnectAsync(config.SmtpServer, config.SmtpPort, socketOptions, ct);
+      var options = ResolveSocketOptions(config.SmtpPort);
+      client.Timeout = config.TimeoutMs;
 
-      if (!string.IsNullOrWhiteSpace(config.SmtpUsername))
+      var addresses = await Dns.GetHostAddressesAsync(config.SmtpServer, ct);
+
+      var ordered = addresses
+                    .OrderByDescending(a => a.AddressFamily == AddressFamily.InterNetwork) // IPv4 first
+                    .ToArray();
+
+      Exception? last = null;
+
+      foreach (var ip in ordered)
       {
-         await client.AuthenticateAsync(config.SmtpUsername, config.SmtpPassword, ct);
+         NetworkStream? stream = null;
+
+         try
+         {
+            using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+            cts.CancelAfter(config.TimeoutMs);
+
+            var socket = new Socket(ip.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
+            await socket.ConnectAsync(new IPEndPoint(ip, config.SmtpPort), cts.Token);
+
+            stream = new NetworkStream(socket, ownsSocket: true);
+
+            await client.ConnectAsync(stream, config.SmtpServer, config.SmtpPort, options, cts.Token);
+
+            stream = null; // MailKit now owns the connection
+
+            await client.AuthenticateAsync(config.SmtpUsername, config.SmtpPassword, cts.Token);
+            return;
+         }
+         catch (Exception ex)
+         {
+            last = ex;
+
+            try
+            {
+               if (stream is not null)
+               {
+                  await stream.DisposeAsync();
+               }
+            }
+            catch
+            {
+               // ignored
+            }
+
+            try
+            {
+               if (client.IsConnected)
+               {
+                  await client.DisconnectAsync(true, CancellationToken.None);
+               }
+            }
+            catch
+            {
+               // ignored
+            }
+         }
       }
+
+      throw last ?? new TimeoutException("SMTP connect failed.");
    }
 
    private static SecureSocketOptions ResolveSocketOptions(int port)

test/Communicator.Demo/appsettings.Development.json

@@ -11,7 +11,7 @@
     "EmailConfigurations": {
       "GeneralSender": {
         "SmtpServer": "smtp.gmail.com",
-        "SmtpPort": "465",
+        "SmtpPort": "587",
         "SmtpUsername": "[email protected]",
         "SmtpPassword": "xemuemnwpcgxcfrh",
         "SenderEmail": "[email protected]",