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Integrate with Twilio

You can use Twilio to embed voice, VoIP, and messaging into applications. In this lab, we will use a Webhook to reply to SMS messages sent to a Twilio phone number. The Webhook is going to be a Knative service running on GKE.

Twilio Setup

You need to create a Twilio account and get a Twilio phone number. You need to make sure that the Twilio number is SMS enabled.

In Twilio console, click on the phone number and go to Messaging section. There's a Webhook defined for when a message comes in. We will change that to our Knative Service later:

Twilio Webhook

Twilio - .NET Core sample

Let's start with creating an empty ASP.NET Core app:

dotnet new web -o twilio-csharp

Inside the twilio-csharp folder, change Startup.cs to use MVC:

public void ConfigureServices(IServiceCollection services)

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    if (env.IsDevelopment())

Next, let's install twilio-aspnet package:

dotnet add package Twilio.AspNet.Core 

Finally, we can create SmsController.cs to receive SMS messages from Twilio:

using Microsoft.AspNetCore.Mvc;
using Twilio.AspNet.Common;
using Twilio.AspNet.Core;
using Twilio.TwiML;

namespace twilio_csharp
    public class SmsController : TwilioController
        public TwiMLResult Index(SmsRequest incomingMessage)
            var messagingResponse = new MessagingResponse();
            messagingResponse.Message("The Knative copy cat says: " + incomingMessage.Body);
            return TwiML(messagingResponse);

SmsController.cs simply echoes back the received message.

Build and push Docker image

Before building the Docker image, make sure the app has no compilation errors:

dotnet build

Create a Dockerfile for the image:

FROM microsoft/dotnet:2.2-sdk

COPY *.csproj .
RUN dotnet restore

COPY . .

RUN dotnet publish -c Release -o out



CMD ["dotnet", "out/twilio-csharp.dll"]

Build and push the Docker image (replace meteatamel with your actual DockerHub):

docker build -t meteatamel/twilio-csharp:v1 .

docker push meteatamel/twilio-csharp:v1

Deploy the Knative service

Create a service.yaml file.

kind: Service
  name: twilio-csharp
  namespace: default
            # Replace meteatamel with your actual DockerHub

After the container is pushed, deploy the app.

kubectl apply -f service.yaml

Check that the service is created:

kubectl get ksvc twilio-csharp
NAME            AGE
twilio-csharp   21s  

Test the service

We can finally test our service by sending an SMS to our Twilio number. We need to setup Twilio Webhook first.

In Twilio console, click on the phone number and go to Messaging section. For Webhook defined for when a message comes in, change it to your Knative service name and NIP.IO domain:

Twilio Webhook

Now, you can send an SMS message to your Twilio number and you should get a reply back from the Knative service!

What's Next?

Deploy to Cloud Run

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