Small demo of how to listen for ZMQ notifications from monerod about txns being added to the mempool

monero-zmq-listen.rs

// Add these to Cargo.toml
// zmq = "0.9.2"
// json = "0.12.4"

use substring::Substring;

async fn start_listening(&self) {
    let context = zmq::Context::new();
    let subscriber = context.socket(zmq::SUB).unwrap();
    subscriber
        .connect("tcp://myxmrnode.com:18085")
        .expect("failed connecting subscriber");
    subscriber.set_subscribe(b"json-minimal-txpool_add").expect("failed subscribing");

    loop {
        subscriber
            .recv_string(0)
            .expect("failed receiving envelope")
            .unwrap();
        let message = subscriber
            .recv_string(0)
            .expect("failed receiving message")
            .unwrap();
        self.process_message(message).await;
    }
}

async fn process_message(&self, msg: String) {
    let prefixlength = "json-minimal-txpool_add:".len();
    let jsonmessage = msg.substring(prefixlength, msg.len());
    let parsed = json::parse(jsonmessage).unwrap();

    println!("Message: {}\tTX Hash: {}", jsonmessage, parsed[0]["id"]);

    // use reqwest to get tx data from monerod using the parsed tx hash
    self.get_tx_data(parsed[0]["id"].to_string()).await;
}