init

src/smtprelay/Smtp/SmtpServer.cs

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+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using System.Net;
+using System.Net.Sockets;
+
+namespace SmtpRelay;
+
+public class SmtpServer(IServiceScopeFactory scopeFactory, ILogger<SmtpServer> logger)
+{
+    private readonly ILogger<SmtpServer> _logger = logger;
+    private readonly IServiceScopeFactory _scopeFactory = scopeFactory;
+
+    public bool IsRunning { get; private set; } = false;
+
+    public async Task RunAsync(SmtpConfig config, CancellationToken cancellationToken)
+    {
+        if (IsRunning) 
+            return;
+
+        var ep = new IPEndPoint(IPAddress.Parse(config.Host), config.Port);
+
+        // start listener
+        using var listener = new TcpListener(ep);
+        listener.Start();
+
+        cancellationToken.Register(listener.Stop);
+
+        // set listener state
+        IsRunning = true;
+
+        // log
+        _logger.LogInformation("SMTP listening on {HOST}:{PORT}", config.Host, config.Port);
+
+        // handler loop
+        while (!cancellationToken.IsCancellationRequested)
+        {
+            try
+            {
+                // await new client
+                var client = await listener.AcceptTcpClientAsync(cancellationToken);
+
+                // handle client async
+                _ = HandleClientAsync(client, config, cancellationToken);
+            }
+            catch (OperationCanceledException) { }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex.ToString());
+            }
+        }
+        
+        // set listener state
+        IsRunning = false;
+    }
+
+    private async Task HandleClientAsync(TcpClient client, SmtpConfig config, CancellationToken cancellationToken)
+    {
+        // create session
+        using var scope = _scopeFactory.CreateScope();
+        var session = scope.ServiceProvider.GetRequiredService<SmtpSession>();
+
+        try
+        {
+            await session.InitAsync(client.Client, config, cancellationToken);
+        }
+        finally
+        {
+            client?.Dispose();
+        }
+    }
+}