Post request in HTTP and HTTPS protocol

We are trying to make a secure communication between our embedded system and web server.Firstly we implement HTTP connection to in our microcontroller. I am just connecting to 80 port of my web server and send simple GET request to this port as example below :

GET /foo.php?msg=test HTTP/1.1
HOST: foo.com

My questions is,How we will turn this to HTTPS ? Which port i should connect ? Will be any difference on structure of GET request above ? Will i have to do some encryption manually or connect to "https" link instead "http" is enuogh for secure communication.

Thanks for any information

Solution

The only difference between a HTTP request and a HTTPS request is that the first is send over a plain TCP connection while the other is send over a TLS connection, i.e.:

with HTTP you establish a TCP connection and send the request over this connection
with HTTPS you establish a TCP connection, upgrade this connection to TLS (including proper certificate validation etc!) and then send the same request as you did with HTTP over this connection.

Apart from that I recommend to either use an established library for HTTP or carefully read the standard. Although HTTP looks simply it is actually not and there are many questions here where users try to do a simply HTTP request and trip over behavior they did not expect.

For example in your case the server might send the response with chunked encoding, with content-length or simply end it with connection close. And it might wait for further requests on the same connection since HTTP/1.1 implicitly enables HTTP keep-alive. Does your code really account for all these cases?