为什么pg_connect（）无法连接到PostgreSQL服务器？

Question

我正在尝试连接到CentOS 6.9上我的应用程序的PostgreSQL数据库：

• 配置页面

<?php
           $host        = "host=1.2.3.4:0000";
           $port        = "port=0000";
           $dbname      = "dbname=some_name";
           $credentials = "user=user_name password=some_password";

?>

• 另一页

<?php
$connection = pg_connect("$host $port $dbname $credentials" ) or die("Could not connect"); 
?>

但是我一直在我的日志文件中收到此消息错误：

PHP Warning:  pg_connect(): Unable to connect to PostgreSQL server: could not connect to server: Connection timed out\n\tIs the server running on host "1.2.3.4" and accepting\n\tTCP/IP connections on port 0000? in /var/www/html/myapp/addmaster.php on line 5, referer: http://a.b.c.d/myapp/index.php