nut-client

A Network UPS Tools (NUT) client library for Rust.

• Connect to upsd/nut-server using TCP
• Login with username and password
• List UPS devices
• List variables for a UPS device
• Connect securely with SSL (optional feature)
• Supports blocking and async (Tokio)

Getting Started

You'll need a running instance of the NUT daemon (upsd, version >= 2.6.4) and a compatible UPS device to use this library:

1. Install NUT
2. Configure and launch upsd

Verify that your UPS is connected using the built-in upsc tool:

upsc myupsname@localhost ups.status

Example

The rupsc CLI is written using this library, and is a clone of NUT's built-in upsc tool.

Below is a sample program using this library (cargo run --example blocking).

You can also run the async version of this code using cargo run --example async --features async-rt (source: nut-client/examples/async.rs).

// nut-client/examples/blocking.rs

use std::env;

use nut_client::blocking::Connection;
use nut_client::{Auth, ConfigBuilder};
use std::convert::TryInto;

fn main() -> nut_client::Result<()> {
    let host = env::var("NUT_HOST").unwrap_or_else(|_| "localhost".into());
    let port = env::var("NUT_PORT")
        .ok()
        .map(|s| s.parse::<u16>().ok())
        .flatten()
        .unwrap_or(3493);

    let username = env::var("NUT_USER").ok();
    let password = env::var("NUT_PASSWORD").ok();
    let auth = username.map(|username| Auth::new(username, password));

    let config = ConfigBuilder::new()
        .with_host((host, port).try_into().unwrap_or_default())
        .with_auth(auth)
        .with_debug(false) // Turn this on for debugging network chatter
        .build();

    let mut conn = Connection::new(&config)?;

    // Print a list of all UPS devices
    println!("Connected UPS devices:");
    for (name, description) in conn.list_ups()? {
        println!("\t- Name: {}", name);
        println!("\t  Description: {}", description);

        // List UPS variables (key = val)
        println!("\t  Variables:");
        for var in conn.list_vars(&name)? {
            println!("\t\t- {}", var);
        }
    }

    Ok(())
}

SSL

You can turn on SSL support by adding .with_ssl(true) in the ConfigBuilder. This requires the ssl feature, which uses rustls under the hood.

Note that, by default, .with_ssl(true) will enable strict verification. This means it will verify the server certificate's DNS entries, check for revocation, and verify the chain using the local root trust. You must also ensure that the connection hostname is a valid DNS name (e.g. localhost, not 127.0.0.1).

If the server is using a self-signed certificate, and you'd like to ignore the strict validation, you can add .with_insecure_ssl(true) along with .with_ssl(true).

Async (Tokio)

The nut-client library supports async network requests. This requires the async feature, which uses Tokio v1 under the hood.

For SSL support, you must use the async-ssl feature as well.