Check this example:
# Translate the combination of Loopback 4 interface address and port 43 in TCP packets to private address 192.168.2.55.
<Huawei> system-view
[Huawei] interface loopback 4
[Huawei-LoopBack4] ip address 192.168.8.8 24
[Huawei-LoopBack4] quit
[Huawei] nat static protocol tcp global interface loopback 4 43 inside 192.168.2.55 netmask 255.255.255.255