PHP SOAP client over IPv4

Question

I have a PHP client that needs to connect to a SOAP server:

$client = new \SoapClient('url_to_wsdl.wsdl', [
                'local_cert' => 'path_to_certificate.pem', 
                'connection_timeout ' => 300,
                'trace' => 1,
            ]);

$params = [];
$response = $client->executeAFunction($params);

But the SOAP client can't connect to the host: SoapFault "Could not connect to host" (it actually can't load the wsdl file either, but I mocked that by using a local copy of the file).

I came to the point where I figured out the Soap client cannot connect to the host because it seemingly uses IPv6 by default (I got to this point because of this answer on SO).

What have I done so far:

I already disabled IPv6 on my server (ubuntu), but that didn't change anything to the SOAP client.

I double-checked the reachability of websites over both IPv4 and IPv6 via the servers terminal

$ curl -6 http://v6.testmyipv6.com/
curl: (6) Could not resolve host: v6.testmyipv6.com

$ curl -4 http://v4.testmyipv6.com/
<html>
<head>
<title>IPv6 Test and Dual-Stack Test For Network Connectivity</title>
...

# the above commands are true for all urls I tested

My actual question is: how can I tell the Soap client to connect to the host using IPv4 instead of using IPv6?

Check the DNS records. If the server isn't reachable over IPv6 then there must not be any AAAA records. — Sander Steffann, Dec 29 '16 at 20:50
@SanderSteffann there is no AAAA record, that is the problem... The system can reach the server but tries to look it up over IPv6 resulting in a 'could not connect to host' fault. — Hans Vn, Dec 30 '16 at 09:28
Clients use IPv6 by default only if there is an IPv6 address known. If there is no IPv6 address then clients fall back to IPv4 unless you force a specific protocol in some other way (like you did with curl). You must be having a different problem. — Sander Steffann, Dec 31 '16 at 07:25

score 2 · Answer 1 · answered Oct 12 '20 at 16:30

Rather than binding to a specific IPv4 IP address, you can also substitute the IP address with 0:

stream_context_create(['socket' => ['bindto' => '0:0']]);

A full example of forcing IPv4 for a SoapClient might be:

$opts = array(
    'http' => array(
        'user_agent' => 'Your/UserAgent'
    ),
    'socket' => ['bindto' => '0:0']
);
$context = stream_context_create($opts);

$soapClientOptions = array(
    'stream_context' => $context,
    'trace' => true,
);
$client = new SoapClient($wsdlUrl, $soapClientOptions);

score 1 · Accepted Answer · answered Jan 15 '18 at 11:58

A SOAP request is a socket connection, so you can use socket_context options. Use stream_context_create() to bind your request to a specified IP.

stream_context_create(['socket' => ['bindto' => '123.123.123.123:0']]);

Set 0 for port number so PHP will set this automatically.

PHP SOAP client over IPv4

2 Answers2