System.Net.WebSockets.WebSocketValidate.ValidateSubprotocol C# (CSharp) Method

        internal static void ValidateSubprotocol(string subProtocol)
        {
            if (string.IsNullOrWhiteSpace(subProtocol))
            {
                throw new ArgumentException(SR.net_WebSockets_InvalidEmptySubProtocol, nameof(subProtocol));
            }

            string invalidChar = null;
            int i = 0;
            while (i < subProtocol.Length)
            {
                char ch = subProtocol[i];
                if (ch < 0x21 || ch > 0x7e)
                {
                    invalidChar = string.Format(CultureInfo.InvariantCulture, "[{0}]", (int)ch);
                    break;
                }

                if (!char.IsLetterOrDigit(ch) &&
                    Separators.IndexOf(ch) >= 0)
                {
                    invalidChar = ch.ToString();
                    break;
                }

                i++;
            }

            if (invalidChar != null)
            {
                throw new ArgumentException(SR.Format(SR.net_WebSockets_InvalidCharInProtocolString, subProtocol, invalidChar), nameof(subProtocol));
            }
        }

        public static WebSocket CreateFromStream(
            Stream stream,
            bool isServer,
            string?subProtocol,
            TimeSpan keepAliveInterval)
        {
            if (stream == null)
            {
                throw new ArgumentNullException(nameof(stream));
            }

            if (!stream.CanRead || !stream.CanWrite)
            {
                throw new ArgumentException(!stream.CanRead ? SR.NotReadableStream : SR.NotWriteableStream, nameof(stream));
            }

            if (subProtocol != null)
            {
                WebSocketValidate.ValidateSubprotocol(subProtocol);
            }

            if (keepAliveInterval != Timeout.InfiniteTimeSpan && keepAliveInterval < TimeSpan.Zero)
            {
                throw new ArgumentOutOfRangeException(nameof(keepAliveInterval), keepAliveInterval,
                                                      SR.Format(SR.net_WebSockets_ArgumentOutOfRange_TooSmall,
                                                                0));
            }

            return(ManagedWebSocket.CreateFromConnectedStream(stream, isServer, subProtocol, keepAliveInterval));
        }