Microsoft.AspNetCore.WebSockets.Protocol.CommonWebSocket.ConnectAsync C# (CSharp) Method

        public async Task ConnectAsync(Uri uri, CancellationToken cancellationToken)
        {
            _state = WebSocketState.Connecting;

            await _connection.ConnectAsync(uri.Host, uri.Port);

            _stream = _connection.GetStream();

            var secKey = Convert.ToBase64String(Encoding.ASCII.GetBytes(Guid.NewGuid().ToString().Substring(0, 16)));
            var expectedAccept = HandshakeHelpers.CreateResponseKey(secKey);

            var headerString =
                $"GET {uri.PathAndQuery} HTTP/1.1\r\n" +
                $"Host: {uri.Host}\r\n" +
                "Connection: Upgrade\r\n" +
                "Upgrade: websocket\r\n" +
                "Sec-WebSocket-Version: 13\r\n" +
                $"Sec-WebSocket-Protocol: {_subProtocol}\r\n" +
                $"Sec-WebSocket-Key: {secKey}\r\n\r\n";

            var bytes = Encoding.UTF8.GetBytes(headerString);
            await _stream.WriteAsync(bytes, 0, bytes.Length, cancellationToken);
            await _stream.FlushAsync(cancellationToken);

            var buffer = new byte[1024];
            var resultLenth = await _stream.ReadAsync(buffer, 0, 1024, cancellationToken);
            var resultString = new StringReader(Encoding.UTF8.GetString(buffer, 0, resultLenth));

            var respCode = 0;
            var headers = new Dictionary<string, string>();
            var line = resultString.ReadLine();
            while (line != null)
            {
                if (line.StartsWith("HTTP/1.1 ") && line.Length > 11)
                    respCode = Convert.ToInt16(line.Substring(9, 3));
                else
                {
                    var items = line.Split(new[] { ':' }, 2);
                    if (items.Length == 2)
                        headers[items[0]] = items[1].TrimStart();
                }

                line = resultString.ReadLine();
            }

            if (respCode != (int) HttpStatusCode.SwitchingProtocols)
            {
                throw new WebSocketException($"The server returned status code '{respCode}' when status code '101' was expected");
            }

            if (!string.Equals(headers["Upgrade"], "WebSocket", StringComparison.OrdinalIgnoreCase)
                || !string.Equals(headers["Connection"], "Upgrade", StringComparison.OrdinalIgnoreCase)
                || !string.Equals(headers["Sec-WebSocket-Accept"], expectedAccept))
            {
                throw new WebSocketException("HTTP header error during handshake");
            }

            _state = WebSocketState.Open;

            if (_keepAliveInterval != Timeout.InfiniteTimeSpan)
            {
                _keepAliveTimer = new Timer(SendKeepAlive, this, _keepAliveInterval, _keepAliveInterval);
            }
        }