problem accessing soap web service's production environment - php

Question

I hope this question won't be marked as duplicate as I read many related questions and answers on the site: although I tried most of the suggestions out there I still couldn't resolve my problem.
My codebase : (I left comments on purpose to give an idea of what I have been trying so far, based on my browsing)
try {
$opts = array(
//~mrossw 'http' => array(
//~mrossw 'user_agent' => 'PHPSoapClient'
//~mrossw ),
//~mrossw 'socket' => array('bindto' => '158.69.189.149')
'socket' => array('bindto' => '127.0.0.1')
//~mrossw ,
//~mrossw 'ssl' => [
//~mrossw 'verify_peer' => true,
//~mrossw 'verify_peer_name' => true,
//~mrossw 'allow_self_signed' => true
//~mrossw ]
);
$context = stream_context_create($opts);
$client = new SoapClient("https://ws_provider_hostname:xxxx/foo/bar/blah/Operaciones/OpFooBarBlahReqABCS?wsdl",
//~mrossw $client = new SoapClient($doc_root.'OpCotizadorVehiculoExtReqABCS.xml',
array(
'location' => "https://ws_provider_hostname:xxxx/foo/bar/blah/Operaciones/OpFooBarBlahReqABCS?wsdl",
'uri' => "https://ws_provider_hostname:xxxx/foo/bar/blah/Operaciones",
// Stuff for development.
'trace' => 1,
'exceptions' => true,
'keep_alive' => true,
'connection_timeout' => 120,
'stream_context' => $context,
'cache_wsdl' => WSDL_CACHE_NONE,
'compression' => SOAP_COMPRESSION_ACCEPT | SOAP_COMPRESSION_GZIP | SOAP_COMPRESSION_DEFLATE,
//~mrossw 'local_cert' => $certRequest_param['sslcertfile'],
//~mrossw 'login'=>'username',
//~mrossw 'password' => 'password'
)
);
} catch (Exception $e) {
echo \"<h2>Exception Error!</h2>\";
echo $e->getMessage();
// print_r($e);
}
The WS provider has an dev environment on port xxxx and a prod env on port yyyy. Hostname and path request are the same.
SoapClient instanciation and operation call work perfect in dev env.
When i change the port to fetch against prod env I get the following error:
SOAP-ERROR: Parsing WSDL: Couldn't load from 'https://ws_provider_hostname:xxxx/foo/bar/blah/Operaciones/OpFooBarBlahReqABCS?wsdl' : failed to load external entity "https://ws_provider_hostname:xxxx/foo/bar/blah/Operaciones/OpFooBarBlahReqABCS?wsdl"
Provider says my public web server's IP is correctly set as allowed in their firewall. It looks right because when I tried to run the code from a different server with different IP and it fails with the same error in both dev and prod env.
When I run that code from a server inside a private network, it works in both
environment ! I don't know much about security, but this sounds to me like a security breach. I mention it here though, in case it can give a clue. I guess this is because this server has a private ip and the provider's firewall don't filter it.
When I go to https://ws_provider_hostname:xxxx/foo/bar/blah/Operaciones/OpFooBarBlahReqABCS?wsdl in my PC browser i get the correct wsdl's xml.
Do you have an idea of what can prevent the code to work form my public web server ?
Or maybe what else can I check ?
For example I couldn't find a way to check the ws server's http response code from outside my browser.
I could neither get a curl request form bash to return the wsdl xml, but that should be another question maybe.
Also let me know if i can provide any other relevant test or data.