Testing the adapter.js example from the web but it prompts error of testitemName not subscribe, any advise?

var net = require('net'),
reqRespStream = net.createConnection(8001, 'localhost'),
notifyStream = net.createConnection(8002, 'localhost'),
metadataStream = net.createConnection(8003, 'localhost');


var MetadataProvider = require('lightstreamer-adapter').MetadataProvider,
DataProvider = require('lightstreamer-adapter').DataProvider,
dataProvider = new DataProvider(reqRespStream, notifyStream),
metadataProvider = new MetadataProvider(metadataStream);

dataProvider.on('subscribe', function(itemName, response) {
//HERE start sending updates for the itemName item
console.log("Subcribed item: " + itemName);
response.success();
});

dataProvider.on('unsubscribe', function(itemName, response) {
//HERE stop sending updates for the itemName item
console.log("Unsubscribed item: " + itemName);
response.success();
});

metadataProvider.on('notifyUserMessage', function(request, response) {
//HERE handle user message
response.success();
});


dataProvider.update("testitemName", false, {
'field1': "valField1",
'field2': "valField2"
});

__________________________________________

C:\Lightstreamer\adapters\NodeAdapter\node_modules \lightstreamer-adapter\lib\dataprovider.js:351
throw new Error('Item [' + itemName + '] is not subscribed');
^
Error: Item [testitemName] is not subscribed
at getIdFromItemName (C:\Lightstreamer\adapters\NodeAdapter\node_module s\lightstreamer-adapter\lib\dataprovider.js:3
51:10)
at EventEmitter.update (C:\Lightstreamer\adapters\NodeAdapter\node_module s\lightstreamer-adapter\lib\dataprovider.js
:300:21)
at Object.<anonymous> (C:\Lightstreamer\adapters\NodeAdapter\adapters.js :30:14)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Function.Module.runMain (module.js:501:10)
at startup (node.js:129:16)
at node.js:814:3