rathole-org/rathole · error

Try to run as a server, but the configuration is missing…

Error message

Try to run as a server, but the configuration is missing. Please add the `[server]` block

What it means

run_server requires the `[server]` section of the TOML configuration to exist because it runs the instance in server mode. When the config has no `server` block, the code in src/server.rs:50 returns this descriptive error instead of a panic, telling the user to add the block.

Solutions

1. Add a `[server]` section with the required settings (bind address, transport, etc.) to the config file.
2. Double-check you are pointing the process at the correct config file (e.g. `--config server.toml`).
3. Compare against the example server config in the repository/docs and add the missing keys.
4. Verify the file parses as expected (no early `[server]` key swallowed by a wrong table).

Example fix

# before (config.toml)
[client]
remote_addr = "example.com:443"

# after
[server]
bind_addr = "0.0.0.0:443"
[transport]
type = "tcp"

let raw = std::fs::read_to_string(config_path)?;
let cfg: toml::Value = toml::from_str(&raw)?;
if cfg.get("server").is_none() {
    anyhow::bail!("config file must contain a [server] block for server mode");
}

When it happens

Trigger: Starting the binary with server role flags (e.g. `--server`) or an entry point that calls run_instance → run_server while the loaded config file lacks a `[server]` section.

Common situations: Using a client-oriented config file for a server deployment; a config file that got truncated or merged incorrectly; copying a minimal client example config and enabling server mode; older configs predating the `[server]` block after a version upgrade.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• Missing tls config
• Missing websocket config
• Neither of `[server]` or `[client]` is defined
• Unknown proxy scheme
• Missing TLS configuration

AI-assisted analysis of rathole-org/rathole@a292f7ed54 (2026-09-07). Data as JSON: /api/errors/a9469322807abe79. Report an issue: GitHub.

Appendix: source

Thrown at src/server.rs:50

type ServiceDigest = protocol::Digest; // SHA256 of a service name
type Nonce = protocol::Digest; // Also called `session_key`

const TCP_POOL_SIZE: usize = 8; // The number of cached connections for TCP servies
const UDP_POOL_SIZE: usize = 2; // The number of cached connections for UDP services
const CHAN_SIZE: usize = 2048; // The capacity of various chans
const HANDSHAKE_TIMEOUT: u64 = 5; // Timeout for transport handshake

// The entrypoint of running a server
pub async fn run_server(
    config: Config,
    shutdown_rx: broadcast::Receiver<bool>,
    update_rx: mpsc::Receiver<ConfigChange>,
) -> Result<()> {
    let config = match config.server {
            Some(config) => config,
            None => {
                return Err(anyhow!("Try to run as a server, but the configuration is missing. Please add the `[server]` block"))
            }
        };

    match config.transport.transport_type {
        TransportType::Tcp => {
            let mut server = Server::<TcpTransport>::from(config).await?;
            server.run(shutdown_rx, update_rx).await?;
        }
        TransportType::Tls => {
            #[cfg(any(feature = "native-tls", feature = "rustls"))]
            {
                let mut server = Server::<TlsTransport>::from(config).await?;
                server.run(shutdown_rx, update_rx).await?;
            }
            #[cfg(not(any(feature = "native-tls", feature = "rustls")))]
            crate::helper::feature_neither_compile("native-tls", "rustls")
        }
        TransportType::Noise => {

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