Using httpClient from a web application results in an error(cakephp3 App On GCE) - cakephp-3.0

Question

I am in great trouble, so I would like you to help me.
I made a web application with cakephp3 and run it on GCE.
When trying to communicate using Http Client, the following error appears.
++++
cakephp version 3.6.2
OS CentOS7 -
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2018-06-20 17:14:19 Error: [Cake\Core\Exception\Exception] fopen(): php_network_getaddresses: getaddrinfo failed: Name or service not known
fopen(https:/XXXX): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known
Request URL: /XXX/?callback=jQuery33100918089472164082_1529482454011
Referer URL: https://{request_host}/XXX/
Stack Trace:
#0 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Client/Adapter/Stream.php(252): Cake\Http\Client\Adapter\Stream->_open(Object(Zend\Diactoros\Uri))
#1 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Client/Adapter/Stream.php(82): Cake\Http\Client\Adapter\Stream->_send(Object(Cake\Http\Client\Request))
#2 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Client.php(430): Cake\Http\Client\Adapter\Stream->send(Object(Cake\Http\Client\Request), Array)
#3 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Client.php(399): Cake\Http\Client->_sendRequest(Object(Cake\Http\Client\Request), Array)
#4 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Client.php(366): Cake\Http\Client->send(Object(Cake\Http\Client\Request), Array)
#5 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Client.php(229): Cake\Http\Client->_doRequest('GET', 'https://{request_host}', NULL, Array)
#6 /usr/local/apache/vhosts/{my_host}/htdocs/src/Controller/Api/XXXController.php(489): Cake\Http\Client->get('https:/request_host}')
#7 /usr/local/apache/vhosts/{my_host}/htdocs/src/Controller/Api/XXXController.php(406): App\Controller\Api\XXXController->__hogeAction('XXX')
#8 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Controller/Controller.php(596): App\Controller\Api\XXXController->invite()
#9 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/ActionDispatcher.php(120): Cake\Controller\Controller->invokeAction()
#10 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/ActionDispatcher.php(94): Cake\Http\ActionDispatcher->_invoke(Object(App\Controller\Api\XXXController))
#11 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/BaseApplication.php(228): Cake\Http\ActionDispatcher->dispatch(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response))
#12 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Runner.php(65): Cake\Http\BaseApplication->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response), Object(Cake\Http\Runner))
#13 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Routing/Middleware/RoutingMiddleware.php(158): Cake\Http\Runner->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response))
#14 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Runner.php(65): Cake\Routing\Middleware\RoutingMiddleware->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response), Object(Cake\Http\Runner))
#15 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Routing/Middleware/AssetMiddleware.php(88): Cake\Http\Runner->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response))
#16 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Runner.php(65): Cake\Routing\Middleware\AssetMiddleware->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response), Object(Cake\Http\Runner))
#17 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Error/Middleware/ErrorHandlerMiddleware.php(98): Cake\Http\Runner->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response))
#18 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Runner.php(65): Cake\Error\Middleware\ErrorHandlerMiddleware->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response), Object(Cake\Http\Runner))
#19 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Runner.php(51): Cake\Http\Runner->__invoke(Object(Cake\Http\ServerRequest), Object(Cake\Http\Response))
#20 /usr/local/apache/vhosts/{my_host}/htdocs/vendor/cakephp/cakephp/src/Http/Server.php(98): Cake\Http\Runner->run(Object(Cake\Http\MiddlewareQueue), Object(Cake\Http\ServerRequest), Object(Cake\Http\Response))
#21 /usr/local/apache/vhosts/{my_host}/htdocs/webroot/index.php(34): Cake\Http\Server->run()
#22 {main}
I checked resolve.conf, but it is colected.
Because it is working properly on my localhost, I think that it is a problem of setting up the server and the network.
I am glad if you can help me. Thank you.

Answer 1

Take a look at the Firewall Rule in the GCP. Make sure that you allow ingress traffic for the ports 80, 443.
Eventually, try to test the URL connection and the ports within the GCE VM instance, or outside the GCP. Below are some examples:
$ curl http://[external-IP-vm-address]:80
$ telnet localhost 80
$ nmap <external-ip-vm-address>
$ netstat -plant
There are other network tests that you could perform. You may consult this discussion thread from Stackexchange.