Sending JSON message to web api via post. Why does HTTP 1.0 versus 1.1 make a difference?
HTTP/1.1 requires you to provide the host name of the server. And it will keep the connection open for some time unless you explicitly opt out of this. Thus, the equivalent of the basic HTTP/1.0 request in HTTP/1.1 language is

POST /the_uri HTTP/1.1
Host: foo.example.com
Connection: close