Проверка Socket.Close();

udpSock.Close();

        private void button_Start_Click(object sender, RoutedEventArgs e)
        {
            Starter();
            viewModel.AddLineToСonsole("UDP сервер запущен...");
        }
 
        private void button_Stop_Click(object sender, RoutedEventArgs e)
        {
            udpSock.Close();
            viewModel.AddLineToСonsole("UDP сервер закрыт.");
        }
 
        public void Starter()
        {
            try
            {
                viewModel.ClearConsole();
                filePath = Environment.CurrentDirectory + "//" + "Data" + "//" + "" + DateTime.Now.ToString("HH_mm_ss") + ".bdi";
                udpSock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
                udpSock.Bind(new IPEndPoint(IPAddress.Any, 10100));
                buffer = new byte[1024];
                EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
                udpSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, udpSock);
            }
            catch (Exception e)
            {
                MessageBox.Show(e.Message);
            }
        }
        private void DoReceiveFrom(IAsyncResult iar)
        {
            try
            {
                Socket recvSock = (Socket)iar.AsyncState;
                EndPoint clientEP = new IPEndPoint(IPAddress.Any, 0);
                int msgLen = recvSock.EndReceiveFrom(iar, ref clientEP);
                byte[] localMsg = new byte[msgLen];
                Array.Copy(buffer, localMsg, msgLen);
                RecordAsync(localMsg, new Head(BitConverter.GetBytes((UInt16)(msgLen + 16)))).GetAwaiter();
                EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
                udpSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, udpSock);
 
                viewModel.AddLineToСonsole("Получено " +msgLen+ " байт с адреса "+((IPEndPoint)clientEP).Address+ ":"+((IPEndPoint)clientEP).Port+"");
 
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    Scroller.ScrollToBottom();
                }));
            }
            catch (ObjectDisposedException)
            {
 
            }
        }

if (IsWorking)
    return;

private CancellationTokenSource? _cts;
 
private async void button_Start_Click(object sender, EventArgs e)
{
    var button = (Button)sender;
    button.Enabled = false;
 
    _cts = new();
    using var udp = new UdpClient(21190);
 
    try { await ProcessMessages(udp, _cts.Token); }
    finally { button.Enabled = true; }
}
 
private void button_Stop_Click(object sender, EventArgs e)
{
    _cts?.Cancel();
    _cts?.Dispose();
    _cts = null;
}
 
private async Task ProcessMessages(UdpClient udp, CancellationToken ct)
{
    await foreach (var message in ReceiveMessages(udp, ct))
    {
        var headLength = BitConverter.GetBytes((ushort)(message.Length + 16));
        await RecordAsync(message, new Head(headLength));
        Scroller.ScrollToBottom();
    }
}   
 
async IAsyncEnumerable<byte[]> ReceiveMessages(UdpClient udp, [EnumeratorCancellation] CancellationToken ct)
{
    UdpReceiveResult result;
    while (!ct.IsCancellationRequested)
    {
        try { result = await udp.ReceiveAsync(ct); }
        catch (OperationCanceledException) { yield break; }
 
        viewModel.AddLineToСonsole($"Получено {result.Buffer.Length} байт с адреса {result.RemoteEndPoint}");
        yield return result.Buffer;
    }
}