Hi kailashb,

as per my understanding, I'am trying to depict the scenario you are going to setup.
You have three different remote Data Providers (let's name them d1, d2, d3) belonging to the same Adapter Set with ID "MyRobustAdapter". So you need to prepare an adapters.xml file, outlined as follows:

Code:
<adapters_conf id="MyRobustAdapter">
    ...
    
    <metadata_provider>
        <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class>
        <param name="request_reply_port">6667</param>
        ...
    </metadata_provider>

    <data_provider name="d1">
        <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class>
        <param name="request_reply_port">6661</param>
        <param name="notify_port">6662</param>
        ...
    </data_provider>
    
    <data_provider name="d2">
        <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class>
        <param name="request_reply_port">6663</param>
        <param name="notify_port">6664</param>
        ...
    </data_provider>
    
    <data_provider name="d3">
        <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class>

        <param name="request_reply_port">6665</param>
        <param name="notify_port">6666</param>
        ...
    </data_provider>

</adapters_conf>
Basically, you will have to define a Robust Proxy Metadata Adapter listening on a specific tcp port for request/reply, and three Robust Proxy Data Adapters each one listening on two different ports for request/reply and notification.
In the example proposed, only basic parameters are shown, but for further details see the comments embedded in the generic adapters.xml file template, you can find in DOCS-SDKs/adapter_remoting_infrastructure/doc/adapter_robust_conf_template/adapters.xml of your Lightstreamer 6 local installation.

A client can connect to all Data Providers, by specifying the Adapter Set ID and Data Providers names. Here a very simple example using the JavaScript Client API:

Code:
// Setup and connect to Lightstreamer Server for using the MyRobustAdapter" Adapter Set.
var ls = new LightstreamerClient(<host>, "MyRobustAdapter");
...
ls.connect();
...

// Setup three subscriptions for each configured Data Provider.
var s1 = new Subscription(<mode>,<items>,<fields>);
s1.setDataAdapter("d1");

var s2 = new Subscription(<mode>,<items>,<fields>);
s2.setDataAdapter("d2");

var s3 = new Subscription(<mode>,<items>,<fields>);
s3.setDataAdapter("d3");

// Submit the subscriptions.
ls.subscribe(s1);
ls.subscribe(s2);
ls.subscribe(s3);
...
Hope this helps, but please get back to us for any doubt.
Gianluca