louislam/uptime-kuma · error · Error

Unable to resolve Steam server hostname "${hostname}": ${err

Error message

Unable to resolve Steam server hostname "${hostname}": ${error.message}

What it means

Thrown from the catch block of resolveSteamHostname() when the underlying dns.lookup call rejects. The original error (ENOTFOUND, EAI_AGAIN, EAI_NONAME, etc.) is captured and re-thrown as a descriptive wrapper so the heartbeat message shows which hostname failed and why.

Source

Thrown at server/monitor-types/steam.js:127

     */
    async resolveSteamHostname(hostname) {
        if (net.isIP(hostname)) {
            return hostname;
        }

        try {
            const lookupResult = await this.lookup(hostname, { all: true });
            const addresses = Array.isArray(lookupResult) ? lookupResult : [lookupResult];
            const ipv4Address = addresses.find(({ address }) => net.isIP(address) === 4);
            const resolvedAddress = ipv4Address?.address || addresses[0]?.address;

            if (!resolvedAddress) {
                throw new Error("DNS lookup returned no addresses");
            }

            return resolvedAddress;
        } catch (error) {
            throw new Error(`Unable to resolve Steam server hostname "${hostname}": ${error.message}`);
        }
    }
}

module.exports = {
    SteamMonitorType,
};

View on GitHub (pinned to 6b5ea01557)

Solutions

Run nslookup/dig for the hostname from the Uptime-Kuma host to reproduce the resolver error.
Fix typos and confirm the hostname is correct and publicly resolvable.
If internal DNS is required, configure the host resolver or /etc/resolv.conf accordingly.
Use the server's IP address directly to eliminate DNS as a variable, then investigate the hostname separately.

Defensive patterns

Strategy: try-catch

Validate before calling

// Cheap pre-check that the hostname is plausible before delegating to dns.lookup.
function isValidHostname(h) { return typeof h === "string" && h.length > 0 && h.length <= 253 && /^[A-Za-z0-9.:-]+$/.test(h); }

Type guard

function isResolvableHost(h) { return !net.isIP(h) && isValidHostname(h); }

Try / catch

try { return await this.lookup(hostname, { all: true }); }
catch (e) { throw new Error(`Unable to resolve Steam server hostname "${hostname}": ${e.message}`, { cause: e }); }

Prevention

Run dig/nslookup on the host before relying on the monitor.
Configure /etc/resolv.conf to a reachable resolver.
Fall back to a literal IP when DNS is flaky.

When it happens

Trigger: Produced when node:dns/promises lookup() throws — hostname does not exist (ENOTFOUND), DNS server timed out (EAI_AGAIN), resolver misconfigured, network down, or a transient resolver failure. Also wraps the 'No addresses' guard from the try-block when the inner throw propagates to the catch.

Common situations: Typo in the Steam server hostname; hostname only resolvable on an internal DNS the Uptime-Kuma host cannot reach; DNS server temporarily unreachable; the hostname was retired; the underlying lookup error 126 ('DNS lookup returned no addresses') is also re-wrapped here because the inner throw is caught.

Related errors

AI-assisted analysis of louislam/uptime-kuma@6b5ea01557 (2026-08-12). Data as JSON: /api/errors/66d8efadb3a7765a. Report an issue: GitHub.