MySQL remote connection takes more than 3 minutes to display result - mysql

Question

I am trying to connect from a local server to my remote server with mysql command...
Result after long delay:
[root#local ~] mysqlshow -u test -p*** -h XXX.XXX.XXX.XXX
ERROR 2013 (HY000): Lost connection to MySQL server at 'reading authorization packet', system error: 0
(The connection is done through my second remote server without any error or delay)
Update 1
Retry connecting from local server after add connect_timeout=500 to the remote server's /etc/my.cnf:
[root#local ~] time mysqlshow -u test -p*** -h XXX.XXX.XXX.XXX
+---------------------+
| Databases |
+---------------------+
| foo |
| bar |
+---------------------+
real 3m21.174s <======== (3m!)
user 0m0.004s
sys 0m0.015s
Successful connection but with more than 3 minutes delay to display the result!
The interesting thing is that when the connection is established, other mysql requests (e.g. mysql> SELECT) take effect immediately!
Update 2
Same result after add skip-host-cache and skip-name-resolve to remote server's /etc/my.cnf...
Update 3
Same request through my second remote server: (Everything seems good)
[root#remote2 ~] time mysqlshow -u test -p*** -h XXX.XXX.XXX.XXX
+---------------------+
| Databases |
+---------------------+
| foo |
| bar |
+---------------------+
real 0m0.016s <======== (0.016s)
user 0m0.007s
sys 0m0.002s
Update 4
Check MySQL Connection from local server with telnet: (Everything seems good!)
[root#local ~] time echo X | telnet -e X XXX.XXX.XXX.XXX 3306
Telnet escape character is 'X'.
Trying XXX.XXX.XXX.XXX...
Connected to XXX.XXX.XXX.XXX.
Escape character is 'X'.
telnet> Connection closed.
real 0m0.136s <======== (0.136s)
user 0m0.000s
sys 0m0.005s
Update 5
Try to connect through PHP mysqli from local server:
<?php
$servername = "XXX.XXX.XXX.XXX";
$username = "test";
$password = "***";
$dbname = "dbname";
$conn = new mysqli( $servername, $username, $password, $dbname );
if( $conn->connect_error ) {
die($conn->connect_error);
}
?>
Result:
Warning: mysqli::__construct(): (HY000/2002): Permission denied in /var/www/html/test.php on line 7
Permission denied
(The PHP mysqli connection is done through the second remote server without any error or delay)
Update 6
Retry with disabled SELinux on the local server solves the PHP connection error but the connection still takes more than 3 minutes!
When the connection is established, other requests (e.g. SELECT) take effect immediately.
Update 7
After trying to connect from local server, On the server's phpMyAdmin (or mysqladmin proc command), new connection added with unauthenticated user...
Update 8
Connection try through XAMPP on windows (from different PC and network) to the remote server:
Same result (connecting with unauthenticated user and more than 3 minutes delay to display results) ...
I'm about to go crazy!!