卷曲失败：无法连接到[servername]端口80：连接超时

Question

以下代码在服务器中运行时显示错误。但此代码适用于本地主机

public function send($url)
        $ch = curl_init();
        curl_setopt($ch,CURLOPT_URL, $url);
        curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);

        $output=curl_exec($ch);
        /*curl_close($ch);
        echo $output;
        return $output;*/
if ($output === FALSE) {
   die("Curl Failed: " . curl_error($ch));
} else {
curl_close($ch);
   return $output;
}

}

显示以下错误

Curl Failed: Failed to connect to [servername] port 80: Connection timed out

请帮帮我