Send Android notifications via .Net Core App

Index

Console Application

Create a new .Net Core empty application and add the Newtonosoft.Json package

Then we define the data types for the message. Notice the JsonProperty to adapt the FCM style of Json data

public class NotificationData
{
    public string ShortDesc { get; set; }
    public long IncidentNo { get; set; }
    public string Description { get; set; }
}

public class Notification
{
    public Notification()
    {
        Sound = "default";
    }

    [JsonProperty("title")]
    public string Title { get; set; }

    [JsonProperty("text")]
    public string Text { get; set; }

    [JsonProperty("sound")]
    public string Sound { get; set; }
}

public class NotificationMessage
{
    [JsonProperty("to")]
    public string To { get; set; }

    [JsonProperty("data")]
    public NotificationData Data { get; set; }

    [JsonProperty("notification")]
    public Notification Notification { get; set; }
}

Then fill the main. The Server key is the one founded inside the FCM console, Settings->Cloud Messaging->Server key

class Program
{
    static void Main(string[] args)
    {
        SendNotificationFromFirebaseCloud();
    }

    public static String SendNotificationFromFirebaseCloud()
    {
        var result = "-1";
        var webAddr = "https://fcm.googleapis.com/fcm/send";
        var httpWebRequest = (HttpWebRequest)WebRequest.Create(webAddr);
        httpWebRequest.ContentType = "application/json";
        httpWebRequest.Headers.Add(HttpRequestHeader.Authorization, "key=PROJECTSETTINGS->Cloud Messagings->Server Key");
        httpWebRequest.Method = "POST";
        using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
        {
            string strNJson = JsonConvert.SerializeObject(new NotificationMessage
            {
                To = "/topics/ServiceNow",
                Data = new NotificationData
                {
                    Description = "Detailed description",
                    IncidentNo = 12345,
                    ShortDesc = "Short desc."
                },
                Notification = new Notification
                {
                    Title = "ServiceNow: Incident No." + 12345,
                    Text = "This is Notification"
                }
            });
            streamWriter.Write(strNJson);
            streamWriter.Flush();
        }

        var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
        using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
        {
            result = streamReader.ReadToEnd();
        }
        return result;
    }
}

Just run and...surprise :) It works!

Adding the API

Add the following nuget packages:
- Microsoft.AspNetCore
- Microsoft.AspNetCore.Hosting
- Microsoft.AspNetCore.Mvc

Now should add the "Web" stuff. The WebStartup class is used to start a web application

public class WebStartup
{
    public IConfiguration Configuration { get; }
    public WebStartup(IConfiguration configuration)
    {
        Configuration = configuration;
    }
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc();
    }
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseMvc();

    }
}

Now change the main to start the application...and quit when needed

class Program
{
    static void Main(string[] args)
    {
        var host = WebHost
            .CreateDefaultBuilder()
            .UseKestrel()
            .UseStartup<WebStartup>()
            .UseUrls("http://*:5006")
            .Build();
        host.Start();

        while (true)
        {
            if ("quit" == Console.ReadLine())
            {
                break;
            }
        }
    }
}

Time then to add the models for our project

public class NotificationModel
{
    public string ShortDesc { get; set; }
    public long IncidentNo { get; set; }
    public string Description { get; set; }
}

public class NotificationResult
{
    public string Result { get; internal set; }
}

And let's add a Controller

[Produces("application/json")]
[Route("api/notifications")]
public class NotificationsController : Controller
{
    [HttpPost]
    [Route("")]
    public NotificationResult Send(NotificationModel messageData)
    {
        var result = "-1";
        var webAddr = "https://fcm.googleapis.com/fcm/send";
        var httpWebRequest = (HttpWebRequest)WebRequest.Create(webAddr);
        httpWebRequest.ContentType = "application/json";
        httpWebRequest.Headers.Add(HttpRequestHeader.Authorization, "key=PROJECTSETTINGS->Cloud Messagings->Server Key");
        httpWebRequest.Method = "POST";
        using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
        {
            string strNJson = JsonConvert.SerializeObject(new NotificationMessage
            {
                To = "/topics/ServiceNow",
                Data = new NotificationData
                {
                    Description = messageData.Description,
                    IncidentNo = messageData.IncidentNo,
                    ShortDesc = messageData.ShortDesc
                },
                Notification = new Notification
                {
                    Title = "ServiceNow: Incident No." + messageData.IncidentNo,
                    Text = "Notification"
                }
            });
            streamWriter.Write(strNJson);
            streamWriter.Flush();
        }

        var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
        using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
        {
            result = streamReader.ReadToEnd();
        }

        return new NotificationResult
        {
            Result = result
        };
    }
    [HttpGet]
    [Route("sanity")]
    public string Sanity()
    {
        return "OK";
    }
}

Now with a simple curl (download here curl for windows) you can send notifications to the phone!

curl --header "Content-Type: application/json" --request POST --data '{"IncidentNo":122,"ShortDesc":"Short incident","Description":"Long description"}' http://localhost:5006/api/notifications

Last modified on: May 08, 2020