how to work with a remote mysql database ??

I got two servers: "www.grupossc.com" with linux and "www.pvtcloudlab.com" with windows

in pvtcloudlab.com the page load his own database but also the mysql databse located in "www.grupossc.com", most of the time the system works without problems, but from time to time the page show you this error:

Warning: mysql_connect(): A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. in C:\Inetpub\vhosts\pvtcloudlab.com\httpdocs\users\Connections\dbnotes1.php on line 16

Fatal error: in C:\Inetpub\vhosts\pvtcloudlab.com\httpdocs\users\Connections\dbnotes1.php on line 16

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that error reffers to this line:
$dbnotes1 = mysql_connect($hostname1, $username1, $password1) or trigger_error(mysql_error(),E_USER_ERROR);

<?php
# FileName="Connection_php_mysql.htm"
# Type="MYSQL"
# HTTP="true"
$hostname_dbnotes = "localhost";
$database_dbnotes = "xxxxxx";
$username_dbnotes = "xxxxxx";
$password_dbnotes = "xxxxxx";
$dbnotes = mysql_connect($hostname_dbnotes, $username_dbnotes, $password_dbnotes) or trigger_error(mysql_error(),E_USER_ERROR); 


$hostname1 = "www.grupossc.com";
$database1 = "xxxxxx";
$username1 = "xxxxxx";
$password1 = "xxxxxx";
$dbnotes1 = mysql_connect($hostname1, $username1, $password1) or trigger_error(mysql_error(),E_USER_ERROR);
?>

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Anyone know why this error happend but just sometimes??? and it is  a way to solve it??????