Zabbix front end cannot connect to zabbix_server

[helpneeder]

I got a error message like this:

• Connection to Zabbix server "127.0.0.1:10051" failed. Possible reasons: 1. Incorrect "NodeAddress" or "ListenPort" in the "zabbix_server.conf" or server IP/DNS override in the "zabbix.conf.php"; 2. Incorrect DNS server configuration. Permission denied

So I deploy the zabbix frontend, server and agent on the same machine, same iP address.
In my zabbix_server.conf, I have NodeAddress=127.0.0.1:10051
and in my zabbix.conf.php, I have ZBX_SERVER = '127.0.0.1'; and ZBX_SERVERPORT = '10051';

The error message says Permission denied, but I have no clue which file's permission is denied.
Please help me!

[DaveS]

Are you running on a Linux server? If you haven't already, I'd check the file owners and permissions

[helpneeder]

I change all the file owners to zabbix, but somehow it still shows the error msg, should I reboot or something?