title: How to use SIM800's AT+HTTPHEAD
body: <p>I want to set the Real Time Clock on my STM32F4 board that I use with a SIM800 modem. I try to send HTTP GET or HEAD request (for example to "google.com") and use the timestamp in the response header to set my RTC.</p>
  
  <p>I can send the request and get the response but I can't read the response's header.</p>
  
  <p>The code is use and the response:</p>
  
  <pre><code>AT+HTTPINIT
  OK
  
  AT+HTTPPARA="CID",1
  OK
  
  AT+HTTPPARA="URL","www.google.com"
  OK
  
  AT+HTTPACTION=0
  OK
  +HTTPACTION: 0,302,256
  
  AT+HTTPHEAD
  ERROR
  </code></pre>
  
  <p>Why I got the ERROR at the end? I tried to send request to another URL, in this case I get HTTP OK(200) and can read data but still can't the header.</p>