Lightstreamer - Basic Chat Demo - Node.js Adapter

The Lightstreamer Basic Chat Demo is a very simple chat application, based on Lightstreamer for its real-time communication needs.

This project contains the source code and all the resources needed to deploy on a Node.js instance the Node.js port of the Lightstreamer - Basic Chat Demo - Java Adapter.

As an example of a client using this adapter, you may refer to the Basic Chat Demo - HTML Client and view the corresponding Live Demo.

Details

This project shows the use of DataProvider and MetadataProvider classes provided in the Lightstreamer SDK for Node Adapters. For more details, see Node.js Interfaces in Lightstreamer - "Hello World" Tutorial - Node.js Adapter

Dig the Code

The project consists of two JavaScript source files:

• nodechat.js, contains the code for the Chat Data and Metadata Adapter;
• robustconnect.js, manages the connection to the Proxy Adapter.

The Adapter Set Configuration

This Adapter Set is configured and will be referenced by the clients as PROXY_NODECHAT. As Proxy Data Adapter and Proxy MetaData Adapter, you may configure also the robust versions. The Robust Proxy Data Adapter and Robust Proxy MetaData Adapter have some recovery capabilities and avoid to terminate the Lightstreamer Server process, so it can handle the case in which a Remote Data Adapter is missing or fails, by suspending the data flow and trying to connect to a new Remote Data Adapter instance. Full details on the recovery behavior of the Robust Data Adapter are available as inline comments within the provided template.

The adapters.xml file for this demo should look like:

<?xml version="1.0"?>

<adapters_conf id="PROXY_NODECHAT">
    <metadata_adapter_initialised_first>N</metadata_adapter_initialised_first>
    
    <metadata_provider>
        <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class>
        <classloader>log-enabled</classloader>
        <param name="request_reply_port">8003</param>
        <param name="timeout">36000000</param>
        <param name="connection_recovery_timeout_millis">10000</param>
    </metadata_provider>
    
    <data_provider name="CHAT_ROOM">
        <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class>
        <classloader>log-enabled</classloader>
        <param name="request_reply_port">8001</param>
        <param name="timeout">36000000</param>
        <param name="connection_recovery_timeout_millis">10000</param>
    </data_provider>
</adapters_conf>

NOTE: not all configuration options of a Proxy Adapter are exposed by the file suggested above. You can easily expand your configurations using the generic template for basic and robust Proxy Adapters as a reference.

Install

If you want to install a version of this demo in your local Lightstreamer Server, follow these steps:

• Download Lightstreamer Server (Lightstreamer Server comes with a free non-expiring demo license for 20 connected users) from Lightstreamer Download page, and install it, as explained in the GETTING_STARTED.TXT file in the installation home directory.
• Get the deploy.zip file of the latest release and unzip it, obtaining the deployment folder.
• Plug the Proxy Data Adapter into the Server: go to the deployment/Deployment_LS folder and copy the ChatAdapterNode directory and all of its files to the adapters folder of your Lightstreamer Server installation.
• Alternatively, you may plug the robust versions of the Proxy Data Adapter: go to the deployment/Deployment_LS(robust) folder and copy the ChatAdapterNode directory and all of its files into the adapters folder.
• Install the lightstreamer-adapter module.
  • Create a directory where to deploy the Node.js Remote Adapter and let call it Deployment_Node_Remote_Adapter.
  • Go to the Deployment_Node_Remote_Adapter folder and launch the commands:
    > npm install lightstreamer-adapter
> npm install command-line-args
    
  • Download the nodechat.js and the robustconnect.js files from this project and copy them into the Deployment_Node_Remote_Adapter folder.
• Launch Lightstreamer Server. The Server startup will complete only after a successful connection between the Proxy Data Adapter and the Remote Data Adapter.
• Launch the Node.js Remote Adapter: go to the Deployment_Node_Remote_Adapter folder and launch:
  > node nodechat.js --host localhost --metadata_rrport 8003 --data_rrport 8001
  
• Test the Adapter, launching the Lightstreamer - Basic Chat Demo - HTML Client listed in Clients Using This Adapter.
  • To make the Lightstreamer - Basic Chat Demo - HTML Client front-end pages get data from the newly installed Adapter Set, you need to modify the front-end pages and set the required Adapter Set name to PROXY_NODECHAT when creating the LightstreamerClient instance. So edit the lsClient.js file of the Basic Chat Demo front-end deployed under Lightstreamer/pages/ChatDemo and replace:
    var lsClient = new LightstreamerClient(protocolToUse+"//localhost:"+portToUse,"CHAT");
    with:
    var lsClient = new LightstreamerClient(protocolToUse+"//localhost:"+portToUse,"PROXY_NODECHAT");
    (you don't need to reconfigure the Data Adapter name, as it is the same in both Adapter Sets).
  • As the referred Adapter Set has changed, make sure that the front-end no longer shares the Engine with other demos. So a line like this:
    lsClient.connectionSharing.enableSharing("ChatDemoCommonConnection", "ATTACH", "CREATE");
    should become like this:
    lsClient.connectionSharing.enableSharing("RemoteChatDemoConnection", "ATTACH", "CREATE");
  • Open a browser window and go to: http://localhost:8080/ChatDemo

Available improvements

Add Encryption

Each TCP connection from a Remote Adapter can be encrypted via TLS. To have the Proxy Adapters accept only TLS connections, a suitable configuration should be added in adapters.xml in the <data_provider> block, like this:

  <data_provider>
    ...
    <param name="tls">Y</param>
    <param name="tls.keystore.type">JKS</param>
    <param name="tls.keystore.keystore_file">./myserver.keystore</param>
    <param name="tls.keystore.keystore_password.type">text</param>
    <param name="tls.keystore.keystore_password">xxxxxxxxxx</param>
    ...
  </data_provider>

and the same should be added in the <metadata_provider> block.

This requires that a suitable keystore with a valid certificate is provided. See the configuration details in the provided template. NOTE: For your experiments, you can configure the adapters.xml to use the same JKS keystore "myserver.keystore" provided out of the box in the Lightstreamer distribution. Since this keystore contains an invalid certificate, remember to configure your local environment to "trust" it. The provided source code is already predisposed for TLS connection on all ports. You can rerun the Node.js Remote Adapter with the new configuration by going to the Deployment_Node_Remote_Adapter folder and launching:
> node nodechat.js --host xxxxxxxx --tls --metadata_rrport 8003 --data_rrport 8001
where the same hostname supported by the provided certificate must be supplied.

Add Authentication

Each TCP connection from a Remote Adapter can be subject to Remote Adapter authentication through the submission of user/password credentials. To enforce credential check on the Proxy Adapters, a suitable configuration should be added in adapters.xml in the <data_provider> block, like this:

  <data_provider>
    ...
    <param name="auth">Y</param>
    <param name="auth.credentials.1.user">user1</param>
    <param name="auth.credentials.1.password">pwd1</param>
    ...
  </data_provider>

and the same should be added in the <metadata_provider> block.

See the configuration details in the provided template. The provided source code is already predisposed for credential submission on both adapters. You can rerun the Node.js Remote Adapter with the new configuration by going to the Deployment_Node_Remote_Adapter folder and launching:
> node nodechat.js --host localhost --user user1 --password pwd1 --metadata_rrport 8003 --data_rrport 8001

Authentication can (and should) be combined with TLS encryption.

See Also

• Lightstreamer SDK for Node Adapters

Clients Using This Adapter

• Lightstreamer - Basic Chat Demo - HTML Client

Related Projects

• Lightstreamer - Basic Chat Demo - Java Adapter
• Lightstreamer - "Hello World" Tutorial - Node.js Adapter

Lightstreamer Compatibility Notes

• Compatible with Lightstreamer SDK for Node.js Adapters version 1.7 or newer and Lightstreamer Server version 7.4 or newer.

• For a version of this example compatible with Lightstreamer Server version since 6.0, please refer to this tag.
• For a version of this example compatible with Lightstreamer SDK for Node.js Adapters version 1.3 to 1.6, please refer to this tag.
• For a version of this example compatible with Lightstreamer SDK for Node.js Adapters version 1.0, please refer to this tag.