[server] How I can realize this scenario

First of all I am sorry for my poor English

My IP information: (em1)
exteal: 217.168.x.x
nameserver1 62.2.x.x
nameserver2 62.2.x.x.
nameserver3 62.2.x.x
nameserver4 62.2.x.x
inteal: 172.30.14.6
gw: 172.30.14.1

This server works without any problem. Now I coected another device (IPTV Stream server). This device has got 2 Etheets.

I can access the server from Inteet with IP:8000
The new device has got web interface and port is 80

I would like to access it from Inteet with 80 and at the same time coect with my server.

Cable coections:
Main server: em1 --->coected and work inteet
Mainserver em2---->IPTV Stream Server Etheet1
Mainserver em3---->IPTV Stream Server Etheet 2

How should I set uo the ifconfig for IPTV Stream to
1.access from Inteet with port 80 via Mainserver
2.send the data to Mainserver through em3

many thanks your helps to in advance