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Blynk server

This document discusses an IOTstack-specific version of Blynk-Server. It is built on top of an Ubuntu base image using a Dockerfile.

References

Acknowledgement:

  • Original writeup from @877dev

Significant directories and files

~/IOTstack
├── .templates
│   └── blynk_server
│       ├── Dockerfile ❶
│       ├── docker-entrypoint.sh ❷
│       ├── iotstack_defaults ❸
│       │   ├── mail.properties
│       │   └── server.properties
│       └── service.yml ❹
├── services
│   └── blynk_server
│       └── service.yml ❺
├── docker-compose.yml ❻
└── volumes
    └── blynk_server ❼
        ├── config ❽
        │   ├── mail.properties
        │   └── server.properties
        └── data
  1. The Dockerfile used to construct Blynk Server on top of Ubuntu.
  2. A start-up script designed to handle container self-repair.
  3. A folder holding the default versions of the configuration files.
  4. The template service definition.
  5. The working service definition (only relevant to old-menu, copied from ❹).
  6. The Compose file (includes ❹).
  7. The persistent storage area for the blynk_server container.
  8. Working copies of the configuration files (copied from ❸).

Everything in ❽:

  • will be replaced if it is not present when the container starts; but
  • will never be overwritten if altered by you.

How Blynk Server gets built for IOTstack

GitHub Updates

Periodically, the source code is updated and a new version is released. You can check for the latest version at the releases page.

IOTstack menu

When you select Blynk Server in the IOTstack menu, the template service definition is copied into the Compose file.

Under old menu, it is also copied to the working service definition and then not really used.

IOTstack first run

On a first install of IOTstack, you run the menu, choose your containers, and are told to do this:

$ cd ~/IOTstack
$ docker-compose up -d

docker-compose reads the Compose file. When it arrives at the blynk_server fragment, it finds:

  blynk_server:
    build:
      context: ./.templates/blynk_server/.
      args:
        - BLYNK_SERVER_VERSION=0.41.16

The build statement tells docker-compose to look for:

~/IOTstack/.templates/blynk_server/Dockerfile

The BLYNK_SERVER_VERSION argument is passed into the build process. This implicitly pins each build to the version number in the Compose file (eg 0.41.16). If you need to update to a

The Dockerfile is in the .templates directory because it is intended to be a common build for all IOTstack users. This is different to the arrangement for Node-RED where the Dockerfile is in the services directory because it is how each individual IOTstack user's version of Node-RED is customised.

The Dockerfile begins with:

FROM ubuntu

The FROM statement tells the build process to pull down the base image from DockerHub.

It is a base image in the sense that it never actually runs as a container on your Raspberry Pi.

The remaining instructions in the Dockerfile customise the base image to produce a local image. The customisations are:

  1. Add packages to satisfy dependencies.
  2. Add the default versions of the configuration files so that the container can perform self-repair each time it is launched.
  3. Download an install the Java package that implements the Blynk Server.

The local image is instantiated to become your running container.

When you run the docker images command after Blynk Server has been built, you may see two rows that are relevant:

$ docker images
REPOSITORY              TAG      IMAGE ID       CREATED         SIZE
iotstack_blynk_server   latest   3cd6445f8a7e   3 hours ago     652MB
ubuntu                  latest   897590a6c564   7 days ago      49.8MB
  • ubuntu is the base image; and
  • iotstack_blynk_server is the local image.

You may see the same pattern in Portainer, which reports the base image as "unused". You should not remove the base image, even though it appears to be unused.

Whether you see one or two rows depends on the version of docker-compose you are using and how your version of docker-compose builds local images.

Logging

You can inspect Blynk Server's log by:

$ docker logs blynk_server

Changing Blynk Server's configuration

The first time you launch the blynk_server container, the following structure will be created in the persistent storage area:

~/IOTstack/volumes/blynk_server
├── [drwxr-xr-x pi      ]  config
│   ├── [-rw-r--r-- pi      ]  mail.properties
│   └── [-rw-r--r-- pi      ]  server.properties
└── [drwxr-xr-x root    ]  data

The two .properties files can be used to alter Blynk Server's configuration. When you make change to these files, you activate then by restarting the container:

$ cd ~/IOTstack
$ docker-compose restart blynk_server

Getting a clean slate

Erasing Blynk Server's persistent storage area triggers self-healing and restores known defaults:

$ cd ~/IOTstack
$ docker-compose down blynk_server
$ sudo rm -rf ./volumes/blynk_server
$ docker-compose up -d blynk_server
Notes:

  • You can also remove individual configuration files and then trigger self-healing. For example, if you decide to edit server.properties and make a mess, you can restore the original default version like this:

    $ cd ~/IOTstack
$ rm volumes/blynk_server/config/server.properties
$ docker-compose restart blynk_server

  • See also if downing a container doesn't work

Upgrading Blynk Server

To find out when a new version has been released, you need to visit the Blynk-Server releases page at GitHub.

At the time of writing, version 0.41.16 was the most up-to-date. Suppose that version 0.41.17 has been released and that you decide to upgrade:

  1. Edit your Compose file to change the version nuumber:

      blynk_server:
    build:
      context: ./.templates/blynk_server/.
      args:
        - BLYNK_SERVER_VERSION=0.41.17

    Note:

    • You can use this method to pin Blynk Server to any available version.

  2. You then have two options:

    • If you only want to reconstruct the local image:

      $ cd ~/IOTstack
$ docker-compose up --build -d blynk_server
$ docker system prune -f

    • If you want to update the Ubuntu base image at the same time:

      $ cd ~/IOTstack
$ docker-compose build --no-cache --pull blynk_server
$ docker-compose up -d blynk_server
$ docker system prune -f
$ docker system prune -f

      The second prune will only be needed if there is an old base image and that, in turn, depends on the version of docker-compose you are using and how your version of docker-compose builds local images.

Using Blynk Server

See the References for documentation links.

Connecting to the administrative UI

To connect to the administrative interface, navigate to:

https://<your pis IP>:9444/admin

You may encounter browser security warnings which you will have to acknowledge in order to be able to connect to the page. The default credentials are:

  • username = admin@blynk.cc
  • password = admin

Change username and password

  1. Click on Users > "email address" and edit email, name and password.
  2. Save changes.

  3. Restart the container using either Portainer or the command line:

    $ cd ~/IOTstack
$ docker-compose restart blynk_server

Setup gmail

Optional step, useful for getting the auth token emailed to you. (To be added once confirmed working....)

iOS/Android app setup

  1. When setting up the application on your mobile be sure to select "custom" setup see.
  2. Press "New Project"
  3. Give it a name, choose device "Raspberry Pi 3 B" so you have plenty of virtual pins available, and lastly select WiFi.
  4. Create project and the auth token will be emailed to you (if emails configured). You can also find the token in app under the phone app settings, or in the admin web interface by clicking Users>"email address" and scroll down to token.

Quick usage guide for app

  1. Press on the empty page, the widgets will appear from the right.
  2. Select your widget, let's say a button.
  3. It appears on the page, press on it to configure.
  4. Give it a name and colour if you want.
  5. Press on PIN, and select virtual. Choose any pin i.e. V0
  6. Press ok.
  7. To start the project running, press top right Play button.
  8. You will get an offline message, because no devices are connected to your project via the token.

Enter Node-Red.....

Node-RED

  1. Install node-red-contrib-blynk-ws from Manage Palette.
  2. Drag a "write event" node into your flow, and connect to a debug node

  3. Configure the Blynk node for the first time:

    URL: wss://youripaddress:9444/websockets

    There is more information here. 4. Enter your auth token from before and save/exit. 5. When you deploy the flow, notice the app shows connected message, as does the Blynk node. 6. Press the button on the app, you will notice the payload is sent to the debug node.