A native OPC UA server for the REX Control System is in development. As soon as we have it ready, I'll let you know. Thanks for your patience.

/*global require,setInterval,console */
var opcua = require("node-opcua");

// Let's create an instance of OPCUAServer
var server = new opcua.OPCUAServer({
    port: 4334, // the port of the listening socket of the server
    resourcePath: "UA/MyLittleServer", // this path will be added to the endpoint resource name
     buildInfo : {
        productName: "MySampleServer1",
        buildNumber: "7658",
        buildDate: new Date(2014,5,2)
    }
});

function post_initialize() {
    console.log("initialized");
    function construct_my_address_space(server) {
   
        var addressSpace = server.engine.addressSpace;
       
        // declare a new object
        var device = addressSpace.addObject({
            organizedBy: addressSpace.rootFolder.objects,
            browseName: "MyDevice"
        });
       
        // add some variables
        // add a variable named MyVariable1 to the newly created folder "MyDevice"
        var variable1 = 1;
       
        // emulate variable1 changing every 500 ms
        setInterval(function(){  variable1+=1; }, 500);
       
        addressSpace.addVariable({
            componentOf: device,
            browseName: "MyVariable1",
            dataType: "Double",
            value: {
                get: function () {
                    return new opcua.Variant({dataType: opcua.DataType.Double, value: variable1 });
                }
            }
        });
       
        // add a variable named MyVariable2 to the newly created folder "MyDevice"
        var variable2 = 10.0;
       
        server.engine.addressSpace.addVariable({
           
            componentOf: device,
           
            nodeId: "ns=1;b=1020FFAA", // some opaque NodeId in namespace 4
           
            browseName: "MyVariable2",
           
            dataType: "Double",   
           
            value: {
                get: function () {
                    return new opcua.Variant({dataType: opcua.DataType.Double, value: variable2 });
                },
                set: function (variant) {
                    variable2 = parseFloat(variant.value);
                    return opcua.StatusCodes.Good;
                }
            }
        });
        var os = require("os");
        /**
         * returns the percentage of free memory on the running machine
         * @return {double}
         */
        function available_memory() {
            // var value = process.memoryUsage().heapUsed / 1000000;
            var percentageMemUsed = os.freemem() / os.totalmem() * 100.0;
            return percentageMemUsed;
        }
        server.engine.addressSpace.addVariable({
           
            componentOf: device,
           
            nodeId: "ns=1;s=free_memory", // a string nodeID
            browseName: "FreeMemory",
            dataType: "Double",   
            value: {
                get: function () {return new opcua.Variant({dataType: opcua.DataType.Double, value: available_memory() });}
            }
        });
    }
    construct_my_address_space(server);
    server.start(function() {
        console.log("Server is now listening ... ( press CTRL+C to stop)");
        console.log("port ", server.endpoints[0].port);
        var endpointUrl = server.endpoints[0].endpointDescriptions()[0].endpointUrl;
        console.log(" the primary server endpoint url is ", endpointUrl );
    });
}
server.initialize(post_initialize);