API, port, and ping monitors

Beyond the checks that run automatically once you add a site, a site's Monitors tab lets you add API and connectivity monitors and manage ICMP ping monitoring for things a plain uptime check can't see. For scheduled jobs and recurring background work, see cron job monitoring.

Choose where a connectivity check runs

An external check runs from DownCTL's servers across the public internet. Use it to answer: “Can a customer or another internet host reach this service?” External API and TCP port monitors must use publicly routable targets; they cannot check private, loopback, or reserved addresses.

An internal connectivity check runs from a connected DownCTL server agent. Use it for a database, cache, VPN-only service, private load balancer, or any host behind a firewall. It can target private addresses such as 10.0.0.5 and internal DNS names such as db.internal, but it only runs while at least one agent for that site is online. Install the agent from the site's Servers section first; see installing the server agent.

Internal monitors support Ping and TCP port checks. When a monitor is due, an active agent for the site claims and runs it, so the agent that records a check can vary if you have multiple servers. The Check now action makes it due for the next agent check-in; it is not a direct connection from DownCTL's servers.

API monitors

Check a specific public HTTP(S) endpoint on a schedule, separate from the site's main uptime check — useful for a health endpoint, an authenticated API route, or a webhook receiver. API monitors always run externally; use an internal TCP or ping monitor when the target is not public.

1. Open a site's Monitors tab and click Add API monitor.
2. Set the method (GET, POST, etc.) and the endpoint path. DownCTL combines that path with the site's URL.
3. Add optional headers and a JSON body when the endpoint requires them.
4. Set expected status codes — the check fails if the response doesn't match. You can also assert a maximum response time, JSON-path presence or value, and text that must or must not appear in the response body.
5. Choose a check interval and timeout.

Failures show up on the dashboard and can trigger an API monitor failing alert rule.

Port monitors

Check that a TCP port is open (or closed, if that's what you expect) — useful for SSH, an SMTP listener, or any non-HTTP service. A TCP connection confirms reachability; it does not verify that the service speaks a particular protocol or accepts a login.

1. From the Infrastructure section of the Monitors tab, click Add connectivity monitor.
2. Select External to check from DownCTL, or Internal (via agent) to check from a server inside your network.
3. Set a label, host, and port number. An external port monitor can leave the host blank to use the site's hostname; its optional host override must stay within the site's domain. An internal monitor accepts any host reachable by its agent.
4. Choose the expected state — open or closed. “Closed” is useful for spotting accidentally exposed administrative services.
5. Choose a check interval.

Port monitor failures can trigger a port monitor down alert rule. Internal check failures can use an internal monitor down alert rule instead.

Ping monitoring

A lighter-weight external ICMP ping check, as an addition to the main HTTP uptime check. It answers whether the site's public hostname responds to ICMP; it does not prove that HTTP, HTTPS, or a specific TCP port works. When you add a site, DownCTL runs an initial ICMP check: if the host responds, ping monitoring stays on; if the host is confirmed unreachable, DownCTL turns it off because many CDNs, load balancers, and firewalls block ICMP even when the website is healthy.

An execution problem on DownCTL's side is recorded as Unknown and does not turn ping monitoring off. Once enabled, ping runs on the same check interval as the site's uptime check. You can turn it on or off at any time from the site's Monitors tab; later failed checks report the failure but do not change that setting. To ping an internal host instead, add an Internal (via agent) connectivity monitor and select Ping.

Vendor dependency monitors

Watch a third-party vendor's own status page — useful when a client site depends on a payment processor, CDN, or hosting provider that could break things outside your control. See third-party and vendor status monitoring for details.