I'm using a NodeMCU, which is connected to an enterprise network at a school. The information given in the GET requests that the ESP8266 sends is sensitive, so naturally we want to make it secure and encrypted - enter SSL. We do the request like so;

HTTPClient http.begin(url, thumbprint)

However, on the network at the school, doing this request fails 90% of the time, so I did a few tests - 100 requests to the exact same IP and certificate, noting how many went through;

  • School network
    • HTTPS requests: 10/100 successful [10%]
    • HTTP requests: 100/100 successful [100%]
  • Private home network
    • HTTPS requests: 100/100 successful [100%]
    • HTTP requests: 100/100 successful [100%]

We have also tried using the WiFiClient class, and while 100% of the requests went through, each one took 15 seconds which is too long.

My question is; what would the problem be, and what can we do to fix it? Can I do something in the code, or on the network?

  • Do you get any error messages?
    – Gerben
    Commented Aug 28, 2018 at 12:47
  • @Gerben No stack errors, the response contains nothing and the HTTP code is -11
    – Albert MN.
    Commented Aug 28, 2018 at 12:48
  • Your school probably uses a proxy which tries to filter out phishing sites or something. It's possible that it only works fast for white-listed domains. Commented Aug 28, 2018 at 12:57
  • I asked about this, and they told me there was nothing blocking my site. Again, it works 10% of the time. They said there was no firewall...
    – Albert MN.
    Commented Aug 28, 2018 at 13:01
  • 1
    Have you tried increasing the timeout (HTTPClient.setTimeout) until you get 100% success?
    – Craig
    Commented Aug 28, 2018 at 16:19

1 Answer 1


Increase the timeout for your request with HTTPClient.setTimeout(). Note the timeout is in milliseconds.

HTTPClient http;
http.setTimeout(15000); // 15 Seconds
http.begin(url, thumbprint);

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