unreachable poller and udp

[sturi]

I have 5 unreachable pollers started and I see that some of them listen to random(?) udp ports. Could those ports be safely firewalled or at the very least fixed to some pre-defined values?

[root@utility zabbix]# netstat -anulp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
16423/zabbix_server
udp        0      0 0.0.0.0:56434           0.0.0.0:*                           16426/zabbix_server
udp        0      0 0.0.0.0:52521           0.0.0.0:*                           16425/zabbix_server
udp        0      0 0.0.0.0:58946           0.0.0.0:*                           16420/zabbix_server

[root@utility zabbix]# ps aux|grep 16423
root     11912  0.0  0.0 112648   972 pts/3    S+   17:12   0:00 grep --color=auto 16423
zabbix   16423  0.0  0.6 382440 24396 ?        S    Mar22   6:44 /usr/sbin/zabbix_server: unreachable poller #4 [got 1 values in 6.009025 sec, getting values]