Micro server, which responds always the same to any GET request

We need a small micro server, which respongs always the same to any GET request with any fields.

The response is a JSON object. it will be empty (that is: '{}'), but with the correct header structure, at least:

Content-Length: 2
Content-Type: application/json; charset=UTF-8

This server is intended to be running on a Raspberry Pi with Raspbian and it needs to be called by URL.

An example using cURL:

curl -H "field1:84:0D:8E:A8:5C:3B" -H "field2:3.10" -H "field3:display" http://update.mypage.com

where http://update.mypage.com should point to the local IP of the Raspberry.

Note: http://update.mypage.com is just an example. It is not the real URL.

Thanks!