According to your description, I guess you may not bind the right IP address for the ip.add.re.ss:8080 domain or use the wrong ip address bind with ip.add.re.ss:8080 domain.
I suggest you could firstly try to use the server's ip address to access your web application to make sure you firewall setting and IP setting is right.
If your client server and the IIS server are in the same domain and you have installed an DNS server, then you could access the web site by domain. Details about how to set the DNS server, you could refer to this article.
If you want to test, you could try to modify the hosts file in the C:\Windows\System32\drivers\etc path in your client server.
For example: 192.168.x.x ip.add.re.ss:8080
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