namespace System.Net.WebSockets
{
    public abstract class WebSocket
    {
        public virtual ValueTask<ValueWebSocketReceiveResult> ReceiveAsync(Buffer<byte> buffer, CancellationToken cancellationToken = default(CancellationToken));
        public virtual Task SendAsync(ReadOnlyBuffer<byte> buffer, CancellationToken cancellationToken = default(CancellationToken));
        …
    }

    [StructLayout(LayoutKind.Auto)]
    public struct ValueWebSocketReceiveResult
    {
        public ValueWebSocketReceiveResult(int count, WebSocketMessageType messageType, bool endOfMessage);
        public ValueWebSocketReceiveResult(int count, WebSocketMessageType messageType, bool endOfMessage, WebSocketCloseStatus? closeStatus, string closeStatusDescription);
        public WebSocketCloseStatus? CloseStatus { get; }
        public string CloseStatusDescription { get; }
        public int Count { get; }
        public bool EndOfMessage { get; }
        public WebSocketMessageType MessageType { get; }
     }
}