How to Use Network Access¶

Accessing the Internet is a common use case for plugins, cBots, and indicators. Previously, algos had to request special permissions to perform any network-related operations, which could raise some concerns from users, especially if these algos were distributed without any source code. Fortunately, cTrader now allows all algos to access web resources without having elevated access rights.

In this video and its corresponding article, we will demonstrate how to retrieve news from a free API that uses JSON for serialisation and deserialisation.

Consuming an API Endpoint¶

In our example, we will use our cBot to read news information from an external source and print it to the log. For this purpose, we will use a free API offered by NewsData.

To check how the API looks like in a browser, we can simply access this link.

https://newsdata.io/api/1/news?apikey=pub_32606381862bbdf07962c72ae7bc6135d6332&&language=en

As we can see, the endpoint provides a sequence of key value pairs that we can easily consume using a cBot. We will begin by adding the namespaces containing several classes and methods for deserialising and reading JSON-formatted data.

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using cAlgo.API;
using cAlgo.API.Collections;
using cAlgo.API.Indicators;
using cAlgo.API.Internals;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Net.Http.Json;
using System.Net.Http;

We can then declare a simple HttpClient() that will access the Internet.

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private static readonly HttpClient client = new HttpClient();

Afterward, we will be able to read data in the OnStart() method.

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protected override void OnStart()
{
    HttpResponseMessage responseToGet = client.GetAsync("https://newsdata.io/api/1/news?apikey=pub_32606381862bbdf07962c72ae7bc6135d6332&q=inflation&language=en").Result;
}

The request will return a raw response in JSON format. We can see how it looks like using a MessageBox.

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var stream = responseToGet.Content.ReadAsStream();
var reader = new StreamReader(stream);
MessageBox.Show(reader.ReadToEnd());

Deserialising JSON Data¶

To deserialise our JSON data, we will use the JsonSerialiser ckass. Before we can do this, however, we will have to define a couple of classes necessary for deserialisation.

• NewsItem. This class will represent a single news article.
• News. This class will contain a collection of NewsItem objects.

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public class NewsItem
{
    public string title { get; set; }   
}

public class News
{
    public List<NewsItem> results { get; set; }
}

If you want to avoid writing this 'boilerplate' code, you can also use an online converter from JSON into C#.

Using the converter, we have defined our classes as follows.

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public class NewsItem
{
    public string article_id { get; set; }
    public string title { get; set; }
    public string link { get; set; }
    public List<string> keywords { get; set; }
    public List<string> creator { get; set; }
    public object video_url { get; set; }
    public string description { get; set; }
    public string content { get; set; }
    public string pubDate { get; set; }
    public string image_url { get; set; }
    public string source_id { get; set; }
    public int source_priority { get; set; }
    public List<string> country { get; set; }
    public List<string> category { get; set; }
    public string language { get; set; }
}

public class News
{
    public string status { get; set; }
    public int totalResults { get; set; }
    public List<NewsItem> results { get; set; }
    public string nextPage { get; set; }
}

We can now write our deserialisation code.

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News news = JsonSerializer.Deserialize<News>(responseToGet.Content.ReadAsStream());

In addition, we can add the following code to print news titles in the log.

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if (responseToGet.IsSuccessful)
{
    News news = JsonSerializer.Deserialize<News>(responseToGet.Body);

    foreach (var item in news.results)
            Print(item.title);
}

If we build and run our cBot, we will see an exception being thrown in the log. However, if we change the access rights of the cBot to AccessRights.FullAccess, we will see that our bot works as intended.

Accessing the Internet Without Elevated Access Rights¶

To avoid having a situation where our cBot needs to request elevated access rights, we can modify our OnStart() method to the following.

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protected override void OnStart()
{
    var responseToGet = Http.Get("https://newsdata.io/api/1/news?apikey=pub_32606381862bbdf07962c72ae7bc6135d6332&q=inflation&language=en");
}

If we set access rights to AccessRights.None and rebuild our cBot, we should see the news titles being printed in the log without any problems. With some more effort, our cBot can be transformed into a fancy news reader available right inside any cTrader chart!

To learn more about the cTrader Algo API, see our documentation or post a question on our forum.