Trying to print from web page (PWA app) using ipp protocol

I'm trying to print raw text from a web page (PWA app). I own a USB printer configured in CUPS on the same machine showing the web page - of course I'm writing Javascript code.
I built a fetch() request like:

fetch('http://'+ip+':'+port+'/printers/'+printer, {
    method: 'POST',
    mode: 'no-cors', 
    headers: {
        'Content-Type': 'application/ipp'
      },
    body: reqBody
    })
.then(response => console.log(response))
.catch(response => console.error(response))

Into the reqBody variable I stored an ipp request.
The response is (from javascript console):

Response {type: "opaque", url: "", redirected: false, status: 0, ok: false, …}
 body: (...)
 bodyUsed: false
 headers: Headers {}
 ok: false
 redirected: false
 status: 0
 statusText: ""
 type: "opaque"
 url: ""

In the Respose view I see the CUPS web page (so HTML code) .. in my understanding it should be ipp data in a HTTP packet, should it?

Where is my error? thanks

The PHP modulre for Apache was not enabled :(