zabbix-sender cant send data to server

[mixmox]

Hello
i have problem with my agent so look into issue deeper and this is the result.
any idea about the problem?

telnet SERVER 10050
Trying SERVER...
Connected to SERVER.
Escape character is '^]'.
Connection closed by foreign host.

telnet SERVER 10051
Trying SERVER...
Connected to SERVER.
Escape character is '^]'.
^]
telnet> quit
Connection closed.

this is telnet result from zabbix server to agent:

telnet AGENT 10050
Trying AGENT...
Connected to AGENT.
Escape character is '^]'.
Connection closed by foreign host.

and

telnet AGENT 10051
Trying AGENT...
telnet: connect to address AGENT: Connection refused
============================
this show that agent can connect to zabbix servers port 10050 and 10051 but still zabbix-sender has error:

zabbix_sender -z SERVER -s "HOSTNAME" -k "sql.restart" -o "0" -vv
zabbix_sender [18503]: DEBUG: In zbx_connect_to_server() [SERVER]:10051 [timeout:60, connection timeout:3]
zabbix_sender [18503]: DEBUG: In zbx_is_ip4() ip:'SERVER'
zabbix_sender [18503]: DEBUG: End of zbx_is_ip4():SUCCEED
zabbix_sender [18503]: DEBUG: Unable to receive from [SERVER]:10051 [ZBX_TCP_READ() timed out]
Sending failed.

[LuzzCG]

Hello,
I know it's been a long time, but did you resolve your issue ?
I have the save problem...
Thanks you