从PHP HTTP客户端调用Amazon上托管的API时,连接被拒绝

我有一个API托管在web服务器上,运行在AmazonEC2端口5001上。当我从chrome浏览器调用API时,它可以工作,但当我从PHP HTTP客户端调用它时,我得到了错误:

Failed to connect to [my public domain].compute.amazonaws.com port 5001: Connection refused

• web服务器在HTTP而不是HTTPS上运行。
• 对于EC2实例安全组,我添加了 Custom TCP
• 当我在其他网站(如www.google.com)上使用相同的HTTP客户端时,效果很好。

<?php
header('Content-Type: application/json');
$url = $_GET['url'];
$ch = curl_init();


curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
$server_output = curl_exec($ch); 

if (curl_errno($ch)) { 
   print curl_error($ch); 
} 
curl_close($ch); 


if ($server_output == "OK") { echo "ok"; } else { echo $server_output; }
?>