TcpClient sometimes needs to wait a few hundred milliseconds to be able to send

Question

Hello everybody. I've got quite a weird problem.

I'm writing a wrapper for TcpClient to send and receive HTTP requests. The main reason I don't use the built-in WebRequest is because I need a support for SOCKS proxies, and WebRequest does not support it.

Anyway, in one of my tests(That use no proxy, just ordinary TcpClient), I've got a weird problem: requests to a certain domain(or to be precise - requiests to coder.io), require a Thread.Sleep of 200 milliseconds to get the stream ready. If I write into the stream without giving the pause, the remote server never returns anything(and than a timeout is thrown).

All other tests on other domains had no such problem ever, but I can never know for sure, as probably there are other servers that will act in a similar manner.

Question is, is there some way to know if a stream is ready to receive data?

Here are a few code snippets:

private Stream GetStream(TcpClient client)
    {
        Stream stream = client.GetStream();
        if (this.IsSsl())
            stream = Ssl.GetSslStream(stream, Uri.Host);
        return stream;
    }
public ExtraWebResponse GetResponse()
    {
        timeoutMillis = Environment.TickCount + Timeout;
        GetGetParams();

        var client = Proxy == null
                         ? new TcpClient(Uri.Host, Port)
                         : Proxy.GetTcpClient(Uri.Host, Port);

        var stream = GetStream(client);
        Thread.Sleep(200);   // Here's the weird part - if I don't include this line - coder.io returns no data.
        try
        {
            var headers = GetHeaders(); //generates HTTP request headers

            using (var writer = new StreamWriter(stream, ContentEncoding ?? Encoding.Default))
            {
                stream.WriteTimeout = timeoutMillis - Environment.TickCount;
                stream.ReadTimeout = timeoutMillis - Environment.TickCount;
                writer.Write(headers);
                writer.Flush();

                var response = new ExtraWebResponse(this);
                var encoding = Encoding.Default;
                bool isEOF;


                response.ReadStatus(ReadLine(stream, encoding, out isEOF)); //reads the response status line
                ReadHeaders(stream, response, encoding); // reads HTTP response headers
                ReadContent(stream, response); //reads the response content

                return response;
            }
        }
        finally
        {
            stream.Close();
        }
    }