Hello Eric,
You will first have to create two subnets one for the guests and one for the internal network, after that a traffic filter will help you with this issue. We can asume that 192.168.1.35 is the server and 192.168.1.0 is the subnet used on your internal network, and you use 192.168.2.0 for guests services
For more details regarding this please check the following guide:
[Huawei-acl-adv-3003] rule 5 permit ip source 192.168.1.0 0.0.0.255 destination 192.168.1.35 0
[Huawei-acl-adv-3003] rule 10 deny ip source 192.168.2.0 0.0.0.255 destination 192.168.1.35 0
[Huawei-acl-adv-3003] quit
[Huawei] wlan
[Huawei-wlan-view] traffic-profile name default
[Huawei-wlan-traffic-prof-default] traffic-filter inbound ipv4 acl 3003
Please let me know after doing the above if you still have issues.