Lightstreamer - Basic Chat Demo - Python 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 a Python 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 Pythhon Adapters. For more details, see Python Interfaces in Lightstreamer - "Hello World" Tutorial - Python Adapter

Dig the Code

The project consists of the chat.py Python module, which contains the code for the Chat Data and Metadata Adapter.

The Adapter Set Configuration

This Adapter Set is configured and will be referenced by the clients as PROXY_PYTHONCHAT. 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_PYTHONCHAT">
    <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 PythonChatAdapter 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 PythonChatAdapter directory and all of its files into the adapters folder.
• Install the Lightstreamer SDK for Python Adapter package, by launching the command:

$ pip install lightstreamer-adapter

• Download the chat.py file from this project.
• 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 Python Remote Adapter, through the command:

$ python chat.py --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_PYTHONCHAT 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_PYTHONCHAT");

  (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. The provided source code is already predisposed for TLS connection on all ports. You can rerun the Python Remote Adapter with the new configuration by launching:

$ python chat.py --host localhost --metadata_rrport 8003 --data_rrport 8001 --tls

where the same hostname supported by the provided certificate must be supplied.

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. As such a keystore contains an invalid certificate, remember to configure your local environment to "trust" it.

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 Python Remote Adapter with the new configuration by launching:

$ python chat.py --host localhost --metadata_rrport 8003 --data_rrport 8001 --user user1 --password pwd1

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

See Also

• Lightstreamer SDK for Python Adapters

Clients Using This Adapter

• Lightstreamer - Basic Chat Demo - HTML Client

Related Projects

• Lightstreamer - Basic Chat Demo - Java Adapter
• Lightstreamer - "Hello World" Tutorial - Python Adapter

Lightstreamer Compatibility Notes

• Compatible with Lightstreamer SDK for Python Adapters version 1.3 or newer and Lightstreamer Server version 7.4 or newer.

• For a version of this example compatible with Lightstreamer Server version since 7.0, please refer to this tag.
• For a version of this example compatible with Lightstreamer SDK for Python Adapters version 1.2, please refer to this tag.