public async Task Ping(CancellationToken token)
{
var payload = Guid.NewGuid().ToByteArray();
var pongSource = new TaskCompletionSource <object>();
token.Register(() => pongSource.TrySetCanceled());
EventHandler <ControlFrameEventArgs> completionTrigger = (sender, e) => {
if ((e.ControlFrame.FrameType == ControlFrame.Type.Pong) &&
payload.SequenceEqual(e.ControlFrame.Payload))
{
pongSource.TrySetResult(null);
}
};
OnControlFrame += completionTrigger;
await WebSocketProtocol.SendControlFrame(OutputStream, new ControlFrame {
Payload = payload,
FrameType = ControlFrame.Type.Ping,
});
// either wait until they read it for us
// or aquire the readlock and read it on our own
var readLockAcquire = InputStream.ManualAcquire();
var pongTask = pongSource.Task;
if (pongTask == await Task.WhenAny(readLockAcquire.Task, pongTask))
{
System.Diagnostics.Debug.WriteLine("nice, they read it for us");
readLockAcquire.Cancel();
}
else
{
System.Diagnostics.Debug.WriteLine("welp, our work");
using (var readLock = await readLockAcquire.Task)
await WebSocketProtocol.ReadFrameGroupLockAcquired(readLock, HandleControlFrame, token, false);
// pls tell me that this was the frame we needed
if (!pongTask.IsCompleted)
{
throw new InvalidDataException("we pinged and they sent something else. welp.");
}
}
OnControlFrame -= completionTrigger;
}
