DearFTP/DearFTP/Connection/StaticDataConnection.cs

using System.IO;
using System.Net;
using System.Net.Security;
using System.Net.Sockets;
using System.Threading.Tasks;

namespace DearFTP.Connection
{
    class StaticDataConnection : IDataConnection
    {
        public const int Timeout = 10_000;

        public Stream Stream { get; private set; }
        public bool IsTlsProtected { get; private set; }

        public int Port => ((IPEndPoint)_listener.LocalEndpoint).Port;
        public bool IsAvailable
        {
            get
            {
                if (_acceptTask == null)
                {
                    return false;
                }
                else if (_acceptTask.Wait(Timeout))
                {
                    return true;
                }
                else
                {
                    _acceptTask.Dispose();
                    _acceptTask = null;
                    return false;
                }
            }
        }

        private static TcpListener _listener;
        private static Task _acceptTask;
        private TcpClient _client;

        public StaticDataConnection()
        {
            if (_listener == null)
            {
                _listener = new TcpListener(IPAddress.Any, FtpServer.Instance.Configuration.Server.ForceDataPort);
                _listener.Start();
            }

            IsTlsProtected = false;
        }

        public void AcceptClient()
        {
            if (_acceptTask?.IsCompleted == false)
            {
                _acceptTask.Wait(Timeout);

                _acceptTask.Dispose();
                _acceptTask = null;
            }

            _acceptTask = _listener.AcceptTcpClientAsync().ContinueWith(t =>
            {
                _client = t.Result;

                if (IsTlsProtected)
                {
                    Stream = new SslStream(_client.GetStream(), false);
                }
                else
                {
                    Stream = _client.GetStream();
                }
            });
        }

        public void Authenticate()
        {
            if (IsTlsProtected)
            {
                ((SslStream)Stream).AuthenticateAsServer(FtpServer.Instance.Configuration.Tls.X509Certificate, false, true);
            }
        }

        public void ActivateTls()
        {
            IsTlsProtected = true;
        }

        public void Close()
        {
            Stream.Close();
            _client.Close();
        }

        public void Create()
        {
            // Nothing to create as the TcpListener is shared by all
        }

        public void DesactivateTls()
        {
            IsTlsProtected = false;
        }

        public static void Stop()
        {
            _listener?.Stop();
        }
    }
}