What are the reasons an HttpWebRequest might take half a minute to get a response?

Question

I'm developing an app for a school project which uses data from CoinGecko's free public API. The way I'm getting the data is with the HttpWebRequest class. At first, I was able to use the API fast, without any problems, but recently the requests have been getting stuck at the GetResponse() function for a long time. Even pinging the API takes about 30 seconds to complete. I've read a lot of posts regarding this problem, and none of the suggestions worked.

try
{
    string uri = "https://api.coingecko.com/api/v3/ping";

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);

    request.Method = "GET";
    request.Accept =
        "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng," +
        "*/*;q=0.8,application/signed-exchange;v=b3;q=0.9";
    request.ContentType = "application/json";
    request.Headers.Add("accept-encoding", "gzip, deflate, br");
    request.Headers.Add("accept-language", "en-US,en;q=0.9");

    request.Headers.Add("cache-control", "max-age=0");
    request.Headers.Add("if-none-match", "W/\"c1f074e1bdf979ac5dc291f2c0acf9e4\"");

    request.Headers.Add("sec-ch-ua", "\" Not A;Brand\"; v = \"99\", \"Chromium\"; v = \"96\", \"Google Chrome\"; v = \"96\"");
    request.Headers.Add("sec-ch-ua-mobile", "?0");
    request.Headers.Add("sec-ch-ua-platform", "\"Windows\"");
    request.Headers.Add("sec-fetch-dest", "document");
    request.Headers.Add("sec-fetch-mode", "navigate");
    request.Headers.Add("sec-fetch-site", "none");
    request.Headers.Add("sec-fetch-user", "?1");
    request.Headers.Add("upgrade-insecure-requests", "1");
    request.UserAgent =
       "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)" +
       " Chrome/97.0.4692.71 Safari/537.36 Edg/97.0.1072.55";
    request.Proxy = null;

    using HttpWebResponse response = (HttpWebResponse)request.GetResponse();

    if (response.StatusCode != HttpStatusCode.OK && response.StatusCode != HttpStatusCode.Created)
    {
        throw new ApplicationException("REST client error code: "
            + response.StatusCode.ToString());
    }

    using Stream stream = response.GetResponseStream();
    if (stream == null)
    {
        throw new ApplicationException("Error: Null response");
    }

    using StreamReader reader = new StreamReader(stream);
    return reader.ReadToEnd();
}
catch (Exception ex)
{
    return ex.ToString();
}

It works with the browser so I copied all the browser request headers and added them to the code but they didn't help. I have also tried: Increasing the number of connections, playing around with all the security protocol types, disabling my firewall. Could it be that the API is detecting and slowing down my requests since they're not "human"?

Answer 1

Set Windows to prioritise IPv4 by typing the following in the command line:

netsh interface ipv6 set prefixpolicy ::ffff:0:0/96 46 4

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