You already found port 52773

IRIS does not have http://localhost:52773/RPCNAME

Where did you get it RPCNAME? How did you configure it in IRIS? What else would you expect it to answer?

I tried to find anything about VistA RPC Broker, and found only an installation guide from 1997, It's a year when Caché was released. 

So, you are asking about VistA RPC Broker on IRIS, I don't know how it's possible 

And why it's an issue with IRIS, not with VistA RPC Broker

xkcd: Standards

FHIR is only a part of the journey, the most important is that so many competing software are already on the market. The issue appears in cases when some applications could get updates and support for anything new, some not. Still, both of them would be required to communicate with each other and it will keep using some way or another some old standards anyway.

This command will only create file CACHE.DAT on Caché, or IRIS.DAT for IRIS, and to be able to see it in portal, you have to create Config.Database as well

But, I would recommend using %Installer Manifest, it's available for many years, and in Caché as well

The simplest installer would look like this

XData setup
  <Default Name="Namespace" Value="IRISAPP"/>
  <Default Name="database" Value="irisapp"/>
  <Namespace Name="${Namespace}" Code="${Namespace}" Data="${Namespace}" Create="yes" Ensemble="no">

      <Database Name="${Namespace}" Dir="${mgrdir}${database}/data" Create="yes" Resource="%DB_${Namespace}"/>

You can find more examples on GitHub