/// <summary>
        ///     Start slave listening for requests.
        /// </summary>
        public override async Task ListenAsync(CancellationToken cancellationToken = new CancellationToken())
        {
            Logger.Information("Start Modbus Tcp Server.");
            // TODO: add state {stopped, listening} and check it before starting
            Server.Start();
            // Cancellation code based on https://stackoverflow.com/a/47049129/11066760
            using (cancellationToken.Register(() => Server.Stop()))
            {
                try
                {
                    while (!cancellationToken.IsCancellationRequested)
                    {
                        TcpClient client = await Server.AcceptTcpClientAsync().ConfigureAwait(false);

                        var masterConnection = new ModbusMasterTcpConnection(client, this, ModbusFactory, Logger);
                        masterConnection.ModbusMasterTcpConnectionClosed += OnMasterConnectionClosedHandler;
                        _masters.TryAdd(client.Client.RemoteEndPoint.ToString(), masterConnection);
                    }
                }
                catch (InvalidOperationException)
                {
                    // Either Server.Start wasn't called (a bug!)
                    // or the CancellationToken was cancelled before
                    // we started accepting (giving an InvalidOperationException),
                    // or the CancellationToken was cancelled after
                    // we started accepting (giving an ObjectDisposedException).
                    //
                    // In the latter two cases we should surface the cancellation
                    // exception, or otherwise rethrow the original exception.
                    cancellationToken.ThrowIfCancellationRequested();
                    throw;
                }
            }
        }
        /// <summary>
        ///     Start slave listening for requests.
        /// </summary>
        public override async Task ListenAsync(CancellationToken cancellationToken = new CancellationToken())
        {
            Logger.Information("Start Modbus Tcp Server.");
            // TODO: add state {stoped, listening} and check it before starting
            Server.Start();

            while (!cancellationToken.IsCancellationRequested)
            {
                TcpClient client = await Server.AcceptTcpClientAsync().ConfigureAwait(false);

                var masterConnection = new ModbusMasterTcpConnection(client, this, ModbusFactory, Logger);
                masterConnection.ModbusMasterTcpConnectionClosed += OnMasterConnectionClosedHandler;
                _masters.TryAdd(client.Client.RemoteEndPoint.ToString(), masterConnection);
            }
        }