Use subxt to connect to any live node

Question

To query Polkadot node with subxt this is the code I used and that works fine.

use subxt::{OnlineClient, SubstrateConfig};

#[subxt::subxt(runtime_metadata_path = "metadata.scale")]
pub mod runtime {}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {

    let api = OnlineClient::<SubstrateConfig>::from_url("wss://rpc.polkadot.io:443").await?;

    let address = runtime::constants().balances().existential_deposit();
    let existential_deposit = api.constants().at(&address)?;
    println!("Existential Deposit: {}", existential_deposit);
    Ok(())
}

The metadata should be the same for common pallets and I used local Astar dev node to fetch metadata with:

subxt metadata -f bytes > metadata.scale

However, when I change rpc url to connect to Kusama, Shiden or Astar I get rpc timeout.

OnlineClient::<SubstrateConfig>::from_url("wss://kusama-rpc.polkadot.io:433").await?;

Error printout:

Error: Rpc(RpcError("Networking or low-level protocol error: Connection timeout exceeded: 10s"))

What is it that I'm doing wrong?

Answer 1

Ah, all right I see you are using the wrong port.

Change the URI to "wss://kusama-rpc.polkadot.io:443" should make it work.

Answer 2

I don't why the nodes you are connecting to are so slow but you could try to increase the connection timeout as follows (you need include jsonrpsee in your Cargo.toml as well):

use subxt::{OnlineClient, SubstrateConfig};
use jsonrpsee::ws_client::WsClientBuilder;
use std::time::Duration;

#[subxt::subxt(runtime_metadata_path = "metadata.scale")]
pub mod runtime {}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let rpc_client = WsClientBuilder::default()
        .connection_timeout(Duration::from_secs(60))
        .build("wss://kusama-rpc.polkadot.io:433")
        .await?;

    let api = SubxtClient::from_rpc_client(rpc_client).await?;

    let address = runtime::constants().balances().existential_deposit();
    let existential_deposit = api.constants().at(&address)?;
    println!("Existential Deposit: {}", existential_deposit);
    Ok(())
}

In addition make sure you compile the program in --release mode