Lightstreamer Node.js Client 9.1.0 API Reference
Summary
Introduction
This Node.js library enables any Node.js application to communicate bidirectionally with the Lightstreamer Server. The API allows to subscribe to real-time data pushed by the server and to send any message to the server.
The library offers automatic recovery from connection failures, automatic selection of the best available transport, and full decoupling of subscription and connection operations. It is responsible of forwarding the subscriptions to the Server and re-forwarding all the subscriptions whenever the connection is broken and then reopened.
The library is distributed through the npm service.
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Note the following documentation convention:
Function arguments qualified as <optional> can be omitted only if not followed by further arguments.
In some cases, arguments that can be omitted (subject to the same restriction) may not be qualified as <optional>, but their optionality will be clear from the description.
Installing
You can install the package lightstreamer-client-node using npm
npm install lightstreamer-client-node
Quickstart
To connect to a Lightstreamer Server, a LightstreamerClient object has to be created, configured, and instructed to connect to the Lightstreamer Server. A minimal version of the code that creates a LightstreamerClient and connects to the Lightstreamer Server on https://push.lightstreamer.com will look like this:
var client = new LightstreamerClient("https://push.lightstreamer.com/","DEMO");
client.connect();
For each subscription to be subscribed to a Lightstreamer Server a Subscription instance is needed. A simple Subscription containing three items and two fields to be subscribed in MERGE mode is easily created (see Lightstreamer General Concepts):
var sub = new Ls.Subscription("MERGE",["item1","item2","item3"],["stock_name","last_price"]);
sub.setDataAdapter("QUOTE_ADAPTER");
sub.setRequestedSnapshot("yes");
client.subscribe(sub);
Before sending the subscription to the server, usually at least one SubscriptionListener is attached to the Subscription instance in order to consume the real-time updates. The following code shows the values of the fields stock_name and last_price each time a new update is received for the subscription:
sub.addListener({
onItemUpdate: function(obj) {
console.log(obj.getValue("stock_name") + ": " + obj.getValue("last_price"));
}
});
Logging
To enable the internal client logger, create a LoggerProvider and set it as the default provider of LightstreamerClient.
var loggerProvider = new ConsoleLoggerProvider(ConsoleLogLevel.DEBUG);
LightstreamerClient.setLoggerProvider(loggerProvider);
Compatibility
The library requires Server 7.4.0.
Documentation
Support
For questions and support please use the Official Forum. The issue list of this page is exclusively for bug reports and feature requests.