301 - This repo was moved to the eagletrt organisation.

eagletrt-ermes

The project that makes remote access to the telemetry very easy.

Project purpose

When the raspberry of the telemetry is connected to the internet, it has not a public IP address and also its local ip is not static. This makes it difficult to access to it locally via ssh and impossible by another net. This project allows exactly that.

The solution

First solution: Ngrok

We firstly used a reverse ssh by using a server with public IP address. The problem was that after a while that server was not anymore available to us, hence we started using ngrok.

You can install ngrok from here and it is needed to be installed only on the raspberry side. We place it in the /usr/local/bin folder and before starting the systemctl service you should first login to ngrok with ./ngrok authtoken [TOKEN], that you find loggin in the ngrok site.

The ngrok is automatically started with a service and opens an ssh tunnel with a certain hostname and port. (Note: the port is usually not 22, hence you should use the -p PORT parameter of the ssh command).

We now suggest to use the zerotier solution instead, but ngrok is still maintained as a second option.

Usage

There is a shell script that calls the api and executes automatically the shell command.

Second solution: Zerotier + mosh

It came out that there where some problems of synchronization of ip with ngrok so we decided to implement a parallel solution which allows us to connect to the rapsberry in an alternative way by using zerotier; moreover to reduce latency we decided to use the ssh wrapper mosh.

Zerotier setup

First of all we sign up to zerotier to be able to create a network. This network is set to private to be able to control accesses and it auto-assigns ip in the 192.168.195.* range.

Then, all clients which want to connect to the created zerotier network need to install zerotier client with curl -s https://install.zerotier.com | sudo bash, although it is installed manually all updates of the service will be managed by apt.

After that you can join the previously created network, which id's can be found in the zerotier dashboard, with sudo zerotier-cli join <network ID>, if you receive an error like zerotier-cli: missing port and zerotier-one.port not found in /var/lib/zerotier-one manually start zerotier-cli with sudo service zerotier-one start and repeat. After authorizing the client throw zerotier dashboard you can see your IP address in the zerotier network with ip addr sh | grep 'inet.*zt'.

Zerotier usage

Now it is possible to connect to all devices in the same network as if they are part of a LAN, for example you can connect via ssh with ssh <username>@<zerotier IP>. All ip's are static within the network so it is not necessary to update the ssh command, moreover it is suggested to login with private/public key instead of using passowrd to do so you can generate keys with ssh-keygen and send them to the server with ssh-copy-id -i <key path> <user>@<server>.

Mosh setup

It is required to install mosh both on client and server with sudo apt-get install mosh. After that you need to disable local variables acceptance form the server, to do so you need to edit /etc/ssh/sshd_config and comment the line AcceptEnv LANG LC_*.

Mosh usage

To connect to a client with mosh use mosh <user>@<server>.

Client and server

Client Nodejs

Another problem was that ngrok did not use always the same hostname and the same port. Hence, we made a client that continuously sends to a server (hosted with heroku) its information. Even if zerotier keeps the same ip, this client is still useful.

The information sent to the server is:

• The local ip address, useful because it is not static.
• The public ip address, I do not know why.
• The ngrok url, in order to use the ssh.
• The zerotier_id, in order to connect to the zerotier network.
• The zerotier_ip, in order to connect to the right ip and have the ssh command.
• The username, for scalability in case of other machines using this client.

The config.default.js file is used by default, but a similar config.js file can be created. The options are:

• RATE_IN_MILLISECONDS: Every how many milliseconds should the client send the information to the server
• GET_PORT_URL: The url that the client uses to get the Ngrok url. This is because ngrok expose an api to get information such as the used address.
• GET_PUBLIC_IP_URL: The url used to get the current public ip address. This is because to know it you should use an api call to an external service.
• GET_ZEROTIER_INFO_COMMAND: The command used to get the information from zerotier.
• POST_PORT_URL: Ther url of the server where you post the machine information.

The client is written in Node.js and uses axios, shelljs and euberlog as external dependencies.

There is also a service that executes the client.

In order to use the client:

1. Clone this repository git clone https://github.com/eagletrt/ermes.
2. Move to the client cd ermes/client/node.
3. Install the dependencies npm install.
4. Only if you need to change the default options, copy the config.default.js file to config.js file by running cp config.default.js config.js.
5. In order to start locally the client run npm start inside the client folder.
6. In order to run it as a service, refer to this file. (Note: it is thought to be used on Ubuntu).

Server

The server is hosted by Heroku and is written with Node.js and express, with handlebars used as view engine. The link of the currently hosted server is https://eagletrt-ermes.herokuapp.com.

The frontend apis are:

• GET /: returns an html page showing the information of the machine telemetria.
• GET /:machine: returns an html page showing the information of the specified machine.

The api apis are:

• GET /api/machines: returns an array of currently stored machines. (This array updates every time a new machine is added by a POST).
• GET /api/machines/:machine: returns the information about the specified machine.
• GET /api/machines/:machine/:field: returns the value of the specified field of the specified machine.
• POST /api/machines/:machine: upserts the machine with the specified information.
• GET /api/eutanasia/receive-death: sets the internal value "shouldDie" to true.
• GET /api/eutanasia: returns the value of "shouldDie" ad sets it to false.

In particular the POST body is something such as:

{
    "ngrokUrl": "tcp://hostname:1234",
    "localIp": "192.168.1.1",
    "publicIp": "340.650.1.1",
    "zerotierId": "xxxxxxx",
    "zerotierIp": "192.168.195.23",
    "user": "ubuntu"
}

While the result of a GET:

{
    "ngrokUrl": "tcp://hostname:1234",
    "ngrokHost": "hostname",
    "ngrokPort": "1234",
    "zerotierId": "xxxxxxx",
    "zerotierIp": "192.168.195.23",
    "zerotierSsh": "ssh username@192.168.195.23",
    "zerotierJoin": "zerotier-cli join xxxxxxx",
    "ssh": "ssh ubuntu@hostname -p 1234", 
    "localIp": "192.168.1.1",
    "publicIp": "340.650.1.1",
    "user": "ubuntu"
}

Site and api

Both the site and the api are served by the url https://eagletrt-ermes.herokuapp.com