182 lines
11 KiB
C#
182 lines
11 KiB
C#
using System.Net;
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using System.Net.Security;
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using System.Net.Sockets;
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using System.Security.Cryptography.X509Certificates;
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using System.Text;
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namespace WpywMail.Native;
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public sealed class SmtpServer
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{
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private readonly AppConfig config;
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private readonly FileStore store;
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private readonly X509Certificate2? certificate;
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private readonly bool advertiseStartTls;
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public SmtpServer(AppConfig config, FileStore store)
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{
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this.config = config;
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this.store = store;
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if (File.Exists(config.TlsCertificatePath)) certificate = new X509Certificate2(config.TlsCertificatePath, config.TlsCertificatePassword);
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advertiseStartTls = certificate is not null && !certificate.Subject.Equals(certificate.Issuer, StringComparison.OrdinalIgnoreCase);
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if (certificate is null) AppLog.Warn("[SMTP] 未找到 TLS 证书；正式公开使用前请配置 TlsCertificatePath。");
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else if (!advertiseStartTls) AppLog.Warn("[SMTP] 当前 TLS 证书是自签名证书，公网收信暂不发布 STARTTLS，避免远端因证书不受信而退信。");
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}
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public async Task RunAsync(CancellationToken cancellationToken)
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{
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var inbound = new TcpListener(IPAddress.Any, config.SmtpPort);
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var submission = new TcpListener(IPAddress.Any, config.SubmissionPort);
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inbound.Start(); submission.Start();
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AppLog.Info($"[SMTP] 收信端口已监听：{config.SmtpPort}");
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AppLog.Info($"[SMTP] 客户端发信端口已监听：{config.SubmissionPort}");
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await Task.WhenAll(AcceptLoop(inbound, false, cancellationToken), AcceptLoop(submission, true, cancellationToken));
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}
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private async Task AcceptLoop(TcpListener listener, bool submission, CancellationToken token)
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{
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try
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{
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while (!token.IsCancellationRequested)
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{
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var client = await listener.AcceptTcpClientAsync(token);
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_ = Task.Run(() => HandleClient(client, submission, token), token);
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}
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}
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catch (OperationCanceledException) { }
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finally { listener.Stop(); }
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}
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private async Task HandleClient(TcpClient client, bool submission, CancellationToken token)
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{
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await using var rawStream = client.GetStream();
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Stream stream = rawStream;
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var reader = NewReader(stream);
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var writer = NewWriter(stream);
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var tls = false;
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string? authenticatedUser = null;
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string? sender = null;
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var recipients = new List<string>();
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var remote = client.Client.RemoteEndPoint?.ToString() ?? "未知地址";
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try
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{
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AppLog.Info($"[SMTP] 收到连接：{remote}，模式={(submission ? "客户端发信" : "公网收信")}");
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await Send(writer, $"220 {config.Hostname} ESMTP WpywMail");
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while (!token.IsCancellationRequested)
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{
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var line = await reader.ReadLineAsync(token);
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if (line is null) break;
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var command = line.Trim();
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var upper = command.ToUpperInvariant();
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if (upper.StartsWith("EHLO") || upper.StartsWith("HELO"))
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{
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await SendMulti(writer, $"250-{config.Hostname}", "250-SIZE 26214400", "250-8BITMIME", "250-PIPELINING", advertiseStartTls && !tls ? "250-STARTTLS" : "250 AUTH LOGIN PLAIN");
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if (advertiseStartTls && !tls) await Send(writer, "250 AUTH LOGIN PLAIN");
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}
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else if (upper == "STARTTLS")
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{
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if (certificate is null || (!submission && !advertiseStartTls)) { await Send(writer, "454 TLS unavailable"); continue; }
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await Send(writer, "220 Ready to start TLS");
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var ssl = new SslStream(stream, false);
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await ssl.AuthenticateAsServerAsync(new SslServerAuthenticationOptions { ServerCertificate = certificate, EnabledSslProtocols = System.Security.Authentication.SslProtocols.Tls12 | System.Security.Authentication.SslProtocols.Tls13 }, token);
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stream = ssl; reader = NewReader(stream); writer = NewWriter(stream); tls = true; authenticatedUser = null;
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}
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else if (upper.StartsWith("AUTH"))
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{
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if (submission && !tls) { await Send(writer, "538 Encryption required for authentication"); continue; }
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authenticatedUser = await Authenticate(command, reader, writer, token);
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await Send(writer, authenticatedUser is null ? "535 Authentication failed" : "235 Authentication successful");
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}
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else if (upper == "RSET")
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{
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sender = null; recipients.Clear(); await Send(writer, "250 Reset");
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}
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else if (upper.StartsWith("MAIL FROM:"))
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{
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sender = ExtractAddress(command); recipients.Clear();
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if (submission && authenticatedUser is null) { AppLog.Warn($"[SMTP] {remote} 未认证就尝试发信：{sender}"); await Send(writer, "530 Authentication required"); }
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else if (submission && !sender.Equals(authenticatedUser, StringComparison.OrdinalIgnoreCase)) { AppLog.Warn($"[SMTP] {remote} 发件人不匹配：{sender}"); await Send(writer, "553 Sender must match authenticated mailbox"); }
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else { AppLog.Info($"[SMTP] {remote} MAIL FROM：{sender}"); await Send(writer, "250 Sender accepted"); }
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}
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else if (upper.StartsWith("RCPT TO:"))
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{
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var recipient = ExtractAddress(command);
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if (sender is null) { AppLog.Warn($"[SMTP] {remote} 未先发送 MAIL FROM 就发送 RCPT TO：{recipient}"); await Send(writer, "503 Need MAIL FROM first"); }
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else if (!submission && !store.IsLocalAddress(recipient)) { AppLog.Warn($"[SMTP] {remote} 非本地收件人被拒绝：{recipient}"); await Send(writer, "550 Relay denied"); }
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else { recipients.Add(recipient); AppLog.Info($"[SMTP] {remote} RCPT TO：{recipient}"); await Send(writer, "250 Recipient accepted"); }
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}
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else if (upper == "DATA")
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{
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if (sender is null || recipients.Count == 0) { await Send(writer, "503 Need sender and recipient"); continue; }
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await Send(writer, "354 End data with <CRLF>.<CRLF>");
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var raw = await ReadData(reader, token);
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var parsed = Mime.Parse(raw);
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if (submission)
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{
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store.QueueOutbound(authenticatedUser!, recipients.ToArray(), parsed.Subject, parsed.Text, raw);
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}
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else
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{
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foreach (var recipient in recipients.Distinct(StringComparer.OrdinalIgnoreCase))
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{
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if (store.FindUser(recipient) is not null)
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store.SaveMessage(new MailMessage { OwnerEmail = recipient.ToLowerInvariant(), Folder = "inbox", From = parsed.From.Length > 0 ? parsed.From : sender, To = recipient, Subject = parsed.Subject, Text = parsed.Text, MessageId = parsed.MessageId, Date = DateTimeOffset.UtcNow, DeliveryStatus = "received" }, raw);
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}
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AppLog.Info($"[SMTP] 已接收邮件：{sender} → {string.Join(", ", recipients)}，主题：{parsed.Subject}");
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}
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await Send(writer, "250 Message queued"); sender = null; recipients.Clear();
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}
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else if (upper == "NOOP") await Send(writer, "250 OK");
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else if (upper == "QUIT") { await Send(writer, "221 Bye"); break; }
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else await Send(writer, "502 Command not implemented");
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}
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}
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catch (Exception ex) when (ex is IOException or SocketException or OperationCanceledException) { }
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catch (Exception ex) { AppLog.Error($"[SMTP] {remote} 会话错误：{ex.Message}"); }
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finally { client.Dispose(); }
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}
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private async Task<string?> Authenticate(string command, StreamReader reader, StreamWriter writer, CancellationToken token)
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{
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var parts = command.Split(' ', 3, StringSplitOptions.RemoveEmptyEntries);
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string? email = null; string? password = null;
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if (parts.Length >= 3 && parts[1].Equals("PLAIN", StringComparison.OrdinalIgnoreCase))
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{
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var bytes = Convert.FromBase64String(parts[2]);
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var values = Encoding.UTF8.GetString(bytes).Split('\0');
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email = values.Length > 1 ? values[1] : null; password = values.Length > 2 ? values[2] : null;
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}
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else if (parts.Length >= 2 && parts[1].Equals("LOGIN", StringComparison.OrdinalIgnoreCase))
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{
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await Send(writer, "334 VXNlcm5hbWU6"); email = Encoding.UTF8.GetString(Convert.FromBase64String(await reader.ReadLineAsync(token) ?? ""));
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await Send(writer, "334 UGFzc3dvcmQ6"); password = Encoding.UTF8.GetString(Convert.FromBase64String(await reader.ReadLineAsync(token) ?? ""));
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}
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else { await Send(writer, "504 Authentication mechanism not supported"); return null; }
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return store.Authenticate(email ?? "", password ?? "")?.Email;
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}
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private static async Task<byte[]> ReadData(StreamReader reader, CancellationToken token)
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{
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var lines = new List<string>();
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while (true)
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{
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var line = await reader.ReadLineAsync(token) ?? ".";
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if (line == ".") break;
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lines.Add(line.StartsWith("..") ? line[1..] : line);
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if (lines.Sum(x => x.Length) > 25 * 1024 * 1024) throw new InvalidOperationException("Message too large");
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}
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return Encoding.UTF8.GetBytes(string.Join("\r\n", lines) + "\r\n");
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}
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private static string ExtractAddress(string command)
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{
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var start = command.IndexOf('<'); var end = command.IndexOf('>', start + 1);
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return start >= 0 && end > start ? command[(start + 1)..end].Trim().ToLowerInvariant() : command[(command.IndexOf(':') + 1)..].Trim().ToLowerInvariant();
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}
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private static StreamReader NewReader(Stream stream) => new(stream, Encoding.UTF8, false, 8192, true);
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private static StreamWriter NewWriter(Stream stream) => new(stream, new UTF8Encoding(false), 8192, true) { AutoFlush = true, NewLine = "\r\n" };
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private static Task Send(StreamWriter writer, string value) => writer.WriteLineAsync(value);
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private static async Task SendMulti(StreamWriter writer, params string[] lines) { foreach (var line in lines) await Send(writer, line); }
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}
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