title: Is `Host` required in HTTP GET request?
body: <p>The following example shows that <code>Host:</code> must be specified. Is this dictated by the HTTP protocol for the GET request or it is just a non-standard feature from <a href="http://httpbin.org" rel="nofollow noreferrer">http://httpbin.org</a>? Thanks.</p>
  
  <pre><code>$ netcat --version 
  netcat (The GNU Netcat) 0.7.1
  Copyright (C) 2002 - 2003  Giovanni Giacobbi
  
  This program comes with NO WARRANTY, to the extent permitted by law.
  You may redistribute copies of this program under the terms of
  the GNU General Public License.
  For more information about these matters, see the file named COPYING.
  
  Original idea and design by Avian Research &lt;hobbit@avian.org&gt;,
  Written by Giovanni Giacobbi &lt;giovanni@giacobbi.net&gt;.
  
  $ sed 's/$/\r/g' &lt;&lt;EOF | netcat -v httpbin.org 80
  GET /get HTTP/1.1
  Host:httpbin.org
  
  EOF
  httpbin.org [23.23.241.244] 80 (http) open
  HTTP/1.1 200 OK
  Connection: keep-alive
  Server: meinheld/0.6.1
  Date: Fri, 09 Feb 2018 14:41:39 GMT
  Content-Type: application/json
  Access-Control-Allow-Origin: *
  Access-Control-Allow-Credentials: true
  X-Powered-By: Flask
  X-Processed-Time: 0.000858068466187
  Content-Length: 157
  Via: 1.1 vegur
  
  {
    "args": {}, 
    "headers": {
      "Connection": "close", 
      "Host": "httpbin.org"
    }, 
    "origin": "165.91.87.88", 
    "url": "http://httpbin.org/get"
  }
  
  $ sed 's/$/\r/g' &lt;&lt;EOF | netcat -v httpbin.org 80
  GET /get HTTP/1.1
  
  EOF
  httpbin.org [54.225.64.197] 80 (http) open
  HTTP/1.1 400 Bad Request
  Connection: close
  Server: Cowboy
  Date: Fri, 09 Feb 2018 14:42:33 GMT
  Content-Length: 0
  </code></pre>