For my Controlling USB on Raspberry Pi project I set up a tunnel using ngrok and had an HTTP listener on the Raspberry Pi using HTTP::Server::Simple. It works very well...

Here is the bit that handles the HTTP requests...

package Bod::Curtains::Server;

VERSION = 1.0

use HTTP::Server::Simple::CGI;
use base qw(HTTP::Server::Simple::CGI);
use Bod::Curtains::Control;
use HTTP::Tiny;
use Sys::Hostname;

use strict;

my $control = Bod::Curtains::Control->new;
my $host = hostname;

sub handle_request {
    my ($self, $request) = @_;
    print "HTTP/1.0 200 OK\r\n";
    print $request->header;
    print "SUCCESS\n";
}
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