Cache 2015 is a very old release. You should update to a latest version at least, preferably to InterSystems IRIS.

InterSystems IRIS natively supports WebSockets protocol as a client (your case) and as a server.

Consider upgrading.

upgrade to 2016.2

What is the reason of this step?

This is a first version with Frozen Plans. If this feature is not needed then upgrade to 2018.1 directly (provided OS compatibility - you're absolutely right about it).

Cache 2017.2 (our App's supported version) turned to be incompatible with Ubuntu 18, which was chosen as on OS for IRIS.

What's the official way to upgrade in that case? I usually just power down an instance, remove it from autostart, upgrade OS to the version supported by a new release, upgrade instance to a new version.

This way Cache/IRIS never runs on unsupported OS. Do you have a case with WRC on this topic?

Yeah I've merged intersystemscommunity org into intersystemsdc recently.

Great to see it used!

Another minor thing:

RESTForms2 link links to localhost and /restforms2-ui/index.html#/

Demo does not work rn

I would also recommend rewriting this property:

Property "cdsm_Physician_Issue_ID" As %String;

like this:

Property physicianIssueID As %String(%JSONFIELDNAME = "cdsm_Physician_Issue_ID");

This way JSON would still be imported, but you would be able to refer to property name without double quotes.

Get 0th array element from your array:

Class test.Provider Extends (%RegisteredObject, %JSON.Adaptor)
{

Property physicianFirstName As %String;

Property physicianLastName As %String;

Property physicianMiddleNameInitial As %String;

Property physicianSpecialty As %String;

Property physicianNPI As %String;

Property physicianMPIN As %String;

Property physicianTaxID As %String;

Property physicianADRId As %String;

Property physicianAddressLine1 As %String;

Property physicianCity As %String;

Property physicianState As %String;

Property physicianZip As %String;

Property physicianZipPlus4 As %String;

Property physicianPhone As %String;

Property facilityNPI As %String;

Property facilityAddressLine1 As %String;

Property facilityCity As %String;

Property facilityState As %String;

Property facilityZip As %String;

Property error As %String(MAXLEN = 200);

Property "cdsm_Physician_Issue_ID" As %String;

ClassMethod GetJSON() [ CodeMode = expression ]
{
[
    {
        "physicianFirstName": "STEVENSON",
        "physicianLastName": "HOWARD",
        "physicianMiddleNameInitial": "W",
        "physicianSpecialty": "null",
        "physicianNPI": "null",
        "physicianMPIN": "null",
        "physicianTaxID": "null",
        "physicianADRId": "null",
        "physicianAddressLine1": "null",
        "physicianCity": "null",
        "physicianState": "null",
        "physicianZip": "null",
        "physicianZipPlus4": "null",
        "physicianPhone": "null",
        "facilityNPI": "null",
        "facilityAddressLine1": "\"\"",
        "facilityCity": "\"\"",
        "facilityState": "\"\"",
        "facilityZip": "\"\"",
        "error": "Invalid NPI. Requested NPI should contain 10 numeric digits",
        "cdsm_Physician_Issue_ID": "null"
    }
]
}

/// do ##class(test.Provider).Test()
ClassMethod Test()
{
    set json = ..GetJSON()
    
    set obj = ..%New()
    set sc = obj.%JSONImport(json.%Get(0))
    
    zw sc,obj
}

}

%ZEN.Auxiliary.jsonProvider class and %ConvertJSONToObject method are definitely available in 2018.1. They are available on way older versions - 2014.1 at least and probably older.

That said, in 2018.1 it would be better to use %ZEN.Auxiliary.altJSONProvider - it has the same methods but uses dynamic objects instead of %ZEN.proxyObject which is faster.

Interesting.

Also check out the Fraud Prevention Demo by  @Amir Samary.

Can you please provide an example?

And the error you're getting.

Check this topic.