raspbi-agent-learning

Join us to learn more on raspberry pi and make some apps using

.NET Core 3.x

• Learn how to build and publish self hosting .NET Core app on Raspberry Pi and run it in the PI itself.
• Learn how to run .NET Core webapi app using Nginx as reverse proxy

Python

• Learn how to implement some basic WebApi using .NET Core
• Learn how to implement some basic WebApi using Python

Mari Mari MARI!!!!

Run a simple .NET Core web app on Raspbian

There are several ways that we can approach to run web apps or web apis' on a Raspbian OS.

1. Self host .NET Core Web Api using Kestrel... the easy way
2. Self host .NET Core Web Api with Nginx in mind

We will try to tackle each of this

1. Self host .NET Core Web Api using Kestrel... the easy way

Follow the steps below

1. Create a simple .NET Core Web Api project. By right you would get a WeatherForecast service in the .NET Core Web Api project template
2. Build and publish it for linux ARM processor in release mode. We will apply self contained web app for this:

dotnet publish -r linux-arm --self-contained true

NOTE: if you set --self-contained false, then you will need to use the dotnet <webapiname> to launch the app

3. Copy the publish folder generated by the dotnet publish command into Raspberry Pi.
4. Run the web app in the Pi.

cd /home/pi/netcore_api_testapp
chmod +x netcore_api
./test

Open Chromium browser, and put in http://localhost:5000.

To automatically run our webapi app automatically you have 2 ways:

1. Run webapi app using auto start in terminal. Refer to this link for more info
2. Run webapi app using systemed functionality

** Primarily we will focus on option (2)

Run webapi app using systemed functionality

1. Create a file in service file

sudo nano /etc/systemed/system/webapi-app.service

add the following contents to it

[Unit]
Description=My Awesome .NET Core WebApi app
 
[Service]
WorkingDirectory=/home/pi/netcore_api_testapp
ExecStart=/home/pi/netcore_api_testapp/netcore_api
Restart=always
# Restart service after 10 seconds if the dotnet service crashes:
RestartSec=10
KillSignal=SIGINT
SyslogIdentifier=netcore_api
User=www-data
Environment=ASPNETCORE_ENVIRONMENT=Production
Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false
 
[Install]
WantedBy=multi-user.target

Save the file.

Run this command:

sudo systemctl enable webapi-app.service
sudo systemctl start webapi-app.service

Open up Chromium browser and navigate to http://localhost:5000. You can also use the commands below to ensure it is working as well

curl http://localhost:5000

and to see the server's output log for this webapi

journalctl -u netcore_api -f

2. Self host .NET Core Web Api with Nginx in mind

Install nginx

sudo apt install nginx
sudo service nginx start

Once installed, replace /etc/nginx/sites-available/default with:

server {
    listen        80;
    server_name   <your host name / public ip>;
    location / {
        proxy_pass         http://localhost:5000;
        proxy_http_version 1.1;
        proxy_set_header   Upgrade $http_upgrade;
        proxy_set_header   Connection keep-alive;
        proxy_set_header   Host $host;
        proxy_cache_bypass $http_upgrade;
        proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header   X-Forwarded-Proto $scheme;
    }
}

Check if the default file is correct

sudo nginx -t
sudo nginx -s reload

Since we are forwarding requests from Nginx to Kestrel and vice versa, and that we have set the proxy_set_header set, we need to modify our webapi app code to match with the proxy header settings In the Startup.cs class file, inside Configure() method, add the following code before the app.UseAuthentication() call.

app.UseForwardedHeaders(new ForwardedHeadersOptions
{
    ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
});

ensure that you publish this webapi app again as per instructions in the earlier section, copy the publish folder over to Pi, then restart the service

sudo systemctl restart webapi-app.service

In your Chromium brower navigate to http://127.0.0.1/swagger. You will find the webapi app is now howsted at port 80 behind nginx.

~~ Python Stuff goes down here

How to Run Flask Python Project

1. Install pip and virtualenv

• virtualenv is a tool to create isolated Python environments. virtualenv creates a folder which contains all the necessary executables to use the packages that a Python project would need.
• To install virtualenv to your machine via pip:

pip install virtualenv

• If you do not have pip installed in your machine, you can refer to this

2. Create virtual environment for your python project

1. Go to your project directory:

cd <your project directory>

2. Create virtual environment using virtualenv

virtualenv <your desired name for virtualenv folder>

--- for example :

virtualenv myproject

3. Activate your virtual environment:

source <name of your virtual environment>/bin/activate

--- for example :

source myproject/bin/activate

Resources for API Server Python

1. Tutorial for Step by steps on developing API Server Python (Flask): Click here
2. Tutorial to add connection to SQL Server with Flask App Python: Click here

Resources for File Transfer to Raspberry Pi

Tutorial for Step by steps on transfering files to raspberry pi:

• Go to raspberrry pi by typing this command in terminal :

sudo raspi-config

• Select Option 5 (Interfacing Options), then choose P2 ( SSH), and Enable SSH Server.
• To enable you to transfer file from your host machine to raspberry pi, you need to install FileZilla Client software to your host machine. More tuturial on how to use FileZilla for transfering files, you can click here.

Files

StackEdit stores your files in your browser, which means all your files are automatically saved locally and are accessible offline!

Create files and folders

The file explorer is accessible using the button in left corner of the navigation bar. You can create a new file by clicking the New file button in the file explorer. You can also create folders by clicking the New folder button.

Switch to another file

All your files and folders are presented as a tree in the file explorer. You can switch from one to another by clicking a file in the tree.

Rename a file

You can rename the current file by clicking the file name in the navigation bar or by clicking the Rename button in the file explorer.

Delete a file

You can delete the current file by clicking the Remove button in the file explorer. The file will be moved into the Trash folder and automatically deleted after 7 days of inactivity.

Export a file

You can export the current file by clicking Export to disk in the menu. You can choose to export the file as plain Markdown, as HTML using a Handlebars template or as a PDF.

Synchronization

Synchronization is one of the biggest features of StackEdit. It enables you to synchronize any file in your workspace with other files stored in your Google Drive, your Dropbox and your GitHub accounts. This allows you to keep writing on other devices, collaborate with people you share the file with, integrate easily into your workflow... The synchronization mechanism takes place every minute in the background, downloading, merging, and uploading file modifications.

There are two types of synchronization and they can complement each other:

• The workspace synchronization will sync all your files, folders and settings automatically. This will allow you to fetch your workspace on any other device.

To start syncing your workspace, just sign in with Google in the menu.

• The file synchronization will keep one file of the workspace synced with one or multiple files in Google Drive, Dropbox or GitHub.

Before starting to sync files, you must link an account in the Synchronize sub-menu.

Open a file

You can open a file from Google Drive, Dropbox or GitHub by opening the Synchronize sub-menu and clicking Open from. Once opened in the workspace, any modification in the file will be automatically synced.

Save a file

You can save any file of the workspace to Google Drive, Dropbox or GitHub by opening the Synchronize sub-menu and clicking Save on. Even if a file in the workspace is already synced, you can save it to another location. StackEdit can sync one file with multiple locations and accounts.

Synchronize a file

Once your file is linked to a synchronized location, StackEdit will periodically synchronize it by downloading/uploading any modification. A merge will be performed if necessary and conflicts will be resolved.

If you just have modified your file and you want to force syncing, click the Synchronize now button in the navigation bar.

Note: The Synchronize now button is disabled if you have no file to synchronize.

Manage file synchronization

Since one file can be synced with multiple locations, you can list and manage synchronized locations by clicking File synchronization in the Synchronize sub-menu. This allows you to list and remove synchronized locations that are linked to your file.

Publication

Publishing in StackEdit makes it simple for you to publish online your files. Once you're happy with a file, you can publish it to different hosting platforms like Blogger, Dropbox, Gist, GitHub, Google Drive, WordPress and Zendesk. With Handlebars templates, you have full control over what you export.

Before starting to publish, you must link an account in the Publish sub-menu.

Publish a File

You can publish your file by opening the Publish sub-menu and by clicking Publish to. For some locations, you can choose between the following formats:

• Markdown: publish the Markdown text on a website that can interpret it (GitHub for instance),

• HTML: publish the file converted to HTML via a Handlebars template (on a blog for example).

Update a publication

After publishing, StackEdit keeps your file linked to that publication which makes it easy for you to re-publish it. Once you have modified your file and you want to update your publication, click on the Publish now button in the navigation bar.

Note: The Publish now button is disabled if your file has not been published yet.

Manage file publication

Since one file can be published to multiple locations, you can list and manage publish locations by clicking File publication in the Publish sub-menu. This allows you to list and remove publication locations that are linked to your file.

Markdown extensions

StackEdit extends the standard Markdown syntax by adding extra Markdown extensions, providing you with some nice features.

ProTip: You can disable any Markdown extension in the File properties dialog.

SmartyPants

SmartyPants converts ASCII punctuation characters into "smart" typographic punctuation HTML entities. For example:

| |ASCII |HTML |

|----------------|-------------------------------|-----------------------------|

|Single backticks|'Isn't this fun?' |'Isn't this fun?' |

|Quotes |"Isn't this fun?" |"Isn't this fun?" |

|Dashes |-- is en-dash, --- is em-dash|-- is en-dash, --- is em-dash|

KaTeX

You can render LaTeX mathematical expressions using KaTeX:

The Gamma function satisfying $\Gamma(n) = (n-1)!\quad\forall n\in\mathbb N$ is via the Euler integral

$$

\Gamma(z) = \int_0^\infty t^{z-1}e^{-t}dt,.

$$

You can find more information about LaTeX mathematical expressions here.

UML diagrams

You can render UML diagrams using Mermaid. For example, this will produce a sequence diagram:

sequenceDiagram

Alice ->> Bob: Hello Bob, how are you?

Bob-->>John: How about you John?

Bob--x Alice: I am good thanks!

Bob-x John: I am good thanks!

Note right of John: Bob thinks a long<br/>long time, so long<br/>that the text does<br/>not fit on a row.

  

Bob-->Alice: Checking with John...

Alice->John: Yes... John, how are you?

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And this will produce a flow chart:

graph LR

A[Square Rect] -- Link text --> B((Circle))

A --> C(Round Rect)

B --> D{Rhombus}

C --> D

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