[root@zabbixproxy01 ~]# tailf /var/log/zabbix/zabbix_proxy.log
2632:20190924:090346.620 cannot send heartbeat message to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2632:20190924:090446.621 cannot send heartbeat message to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2633:20190924:090527.274 cannot send proxy data to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2632:20190924:090546.622 cannot send heartbeat message to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2633:20190924:091609.406 cannot send proxy data to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2632:20190924:091746.867 cannot send heartbeat message to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2632:20190924:092346.950 cannot send heartbeat message to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2631:20190924:092447.037 received configuration data from server at "Zabbix Server Address FQDN", datalen 881974
2633:20190924:092624.209 cannot send proxy data to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out
2632:20190924:092746.989 cannot send heartbeat message to server at "Zabbix Server Address FQDN": ZBX_TCP_READ() timed out