resolved: shall not put "\r\n" characters into the string but like this:

> POST /test_json.php HTTP/1.1
Host: test.myserver.com
Content-Type: application/json
Content-length: 11

{"test": 3}

I need correct syntax to use AT+CIPSEND command in order to send HTTP POST request.

First I send:
AT+CIPSTART="TCP","test.myserver.com",80

CONNECT
OK

Then:
AT+CIPSEND=130

When I get the prompt I send something like:
> POST /test_json.php HTTP/1.1\r\nHost: test.myserver.com\r\nContent-Type ...