Agent's Status: not available

[tge]

Hello all.

I installed zabbix 1.8 on CentOS5.4.

ZABBIX Server's status is available but agent status is not available with the following error:
"Got empty string from [xxx.xxx.xxx.128]. Assuming that agent dropped connection because of access permissions"

xxx.xxx.xxx.128 is my zabbix server&agent address.

I can reached 10050&10051 port on this server by telnet.

/etc/zabbix/zabbix_agentd.conf
Server=xxx.xxx.xxx.128
ServerPort=10050
Hostname=xxx.xxx.xxx.128
#ListenPort=10050
#ListenIP=xxx.xxx.xxx.128

/etc/zabbix/zabbix_server.conf
#ListenIP=xxx.xxx.xxx.128

2nd problem is with other monitored server.
Error message is "Get value from agent failed: Cannot resolve"

ZABBIX server(xxx.xxx.xxx.128) is the same as above.
Host server(installed zabbix agent) is xxx.xxx.xxx.129.

/etc/zabbix/zabbix_agentd.conf
Server=xxx.xxx.xxx.128
Hostname=xxx.xxx.xxx.128
ListenPort=10060
ListenIP=xxx.xxx.xxx.129

This host server has an item for icmpping by simple check.

How can i monitor the agents??
Firewall and selinux are disabled.

Thank you.