Tutorials

Show current position from demo.signalk.org

In this tutorial we will make a sample client that connects to the SignalK demo server using the REST Api and shows the current position of the self target.

This tutorial assumes that you have cargo installed and working on the command line, a nice tutorial on the first steps in cargo can be found in the cargo book.

This tutorial so far have only been tested on Ubuntu (22.04 Jammy).

Create your signalk project

Prepare your development host for ssl-library content:

sudo apt install libssl-dev

Now we can set up a new rust project with the cargo command

cargo new sk_position
cd sk_position

This will crate a sample application. Cargo will make a sample hello_world application in main.rs. We will soon change that into an application that connects to SignalKs demo server and shows the position of the self ship.

Nest we need to add dependencies to the rust dependencies that we need in our code.

• signalk - The SignalK data library

• reqwest - A http (REST) client library

• tokio - The async driver to make the async REST calls

cargo add signalk
cargo add reqwest -F json
cargo add tokio -F full

Now we are ready to make out first API call to the demo-server.

Update the main.rs file to contain the following code:

use signalk::V1FullFormat;
use reqwest::Error;


#[tokio::main]
async fn main() -> Result<(), Error> {
    let api_url = "https://demo.signalk.org/signalk/v1/api/";
    println!("Connect and get data from: {}", api_url);
    let response = reqwest::get(api_url).await?;
    let sk_data: V1FullFormat = response.json().await?;
    if let Some(self_vessel) = sk_data.get_self() {
        if let Some(ref nav) = self_vessel.navigation {
            if let Some(ref pos) = nav.position {
                print!("Position: lat {} long {}",
                       pos.value.latitude, pos.value.longitude);
            }
        }
    }
    Ok(())
}

We can now run the application towards the demo.api and see the result:

cargo run