Sony Arouje

Last couple of hours I was working on a small .NET client library to connect to Meteor js application using Distributed Data Protocol (DDP). This post will give some insight to the library I am working on. You can see more details of DDP here.

Using DDPClient.NET you can subscribe to published items or call a Meteor method and display the same in your ASP.NET or Desktop applications.

First let’s go through the server code in my meteor application.

if(Meteor.is_server)
{
    Meteor.publish("allproducts", function(){
        return Products.find();
    });

    Meteor.startup(function(){
        console.log("starting Point of sale application.....");
      });

    Meteor.methods({
        addProduct: function (prodCode, prodDesc) {
            return "Product Name: " + prodDesc + " Product Code: " + prodCode;
        }

    });
}

From the Meteor application we are publishing an item called ‘allproducts’ and have a server method called ‘addProduct’ that takes two parameters. Now let’s see how to subscribe to published item and call the server method using DDPClient.NET.

Subscribe to Published items

class Program
{
    static void Main(string[] args)
    {
        IDataSubscriber subscriber = new Subscriber();
        DDPClient client = new DDPClient(subscriber);

        client.Connect("localhost:3000");
        client.Subscribe("allproducts");
    }

}

public class Subscriber:IDataSubscriber
{
    public void DataReceived(dynamic data)
    {
        try
        {
            if (data.type == "sub")
            {
                Console.WriteLine(data.prodCode + ": " + data.prodName + 

                                         ": collection: " + data.collection);
            }
        }
        catch(Exception ex)
        {
            throw;
        }
    }
}

As you can see it’s very easy to connect to Meteor application using DDPClient.NET. Just call the Connection function with the url. Then call the subscribe function to subscribe to any published item in Meteor application.

In the above code I subscribed to ‘allproducts’ item. After you subscribed successfully to the meteor application, we will receive all the products stored in the db. Once our client is subscribed any insert/delete/update will streamed to the .NET client. You can test it by adding a some products via the web application and you can see the newly added product get displayed in the console.

How to call a Meteor Method?

class Program
{
    static void Main(string[] args)
    {
        IDataSubscriber subscriber = new Subscriber();
        DDPClient client = new DDPClient(subscriber);

        client.Connect("localhost:3000");
        client.Call("addProduct", "NS5", "IRobot");
        Console.ReadLine();
    }
}

public class Subscriber:IDataSubscriber
{
    public void DataReceived(dynamic data)
    {
        try
        {
            if (data.type == "method")
                Console.WriteLine(data.result);
        }
        catch(Exception ex)
        {
            throw;
        }
    }
}

As you can see the Meteor method ‘addProduct’ take two arguments prodCode and prodDesc. So when we call the method we have to pass the parameter as well. We can do that by invoking the ‘Call’ function with the method name and arguments as shown below.

client.Call(“addProduct”, “NS5”, “IRobot”);

Also you will get notification if any data get deleted from the database. You can check the same as shown below.

else if (data.type == "unset")
{
    Console.WriteLine("deleleted item with id: " + data.id); 

}

so you will get the id of the data it deleted, you can search for the product with this id and remove or do what ever you wanted to do.

DDPClient.NET is checked into Github. The meteor code I referred here is added to the one I used in  Getting Started with meteor.