Ping, TCP & DNS monitors

Monitor host reachability with ICMP, check TCP port availability, and validate DNS records.

These three monitor types cover low-level network health checks: ICMP reachability, TCP port availability, and DNS record validation.

Ping monitor

Ping monitors send ICMP packets to one or more hosts and evaluate the combined result.

Configuration

Field	Type	Default	Notes
hosts	Array<{ type, host, timeout, count }>	one empty host row	At least one host required
pingEval	string (JS function)	built-in default	Optional custom eval

Host fields:

Field	Type	Default	Notes
type	IP4 | IP6 | DOMAIN	IP4	Address type
host	string	—	Required
timeout	number	1000	Timeout per ping attempt in ms
count	number	3	Number of ICMP packets to send

Default eval behavior

• UP if all hosts respond (alive === true)
• DOWN if any host is unreachable
• Latency = average latency across all hosts

The built-in eval function:

async function (arrayOfPings) {
    let latencyTotal = arrayOfPings.reduce((acc, ping) => {
        return acc + ping.latency;
    }, 0);

    let alive = arrayOfPings.reduce((acc, ping) => {
        return acc && ping.alive;
    }, true);

    return {
        status: alive ? 'UP' : 'DOWN',
        latency: latencyTotal / arrayOfPings.length,
    }
}

Custom eval contract

Your function receives arrayOfPings and must return { status, latency }.

Example

{
    "type": "PING",
    "type_data": {
        "hosts": [
            { "type": "IP4", "host": "8.8.8.8", "timeout": 1000, "count": 3 }
        ]
    }
}

Troubleshooting

• Frequent DOWN: some networks and firewalls block ICMP — consider switching to a TCP check on the same host
• Noisy latency: increase count to reduce the effect of a single dropped packet
• Validation error: the type field must match the format of the address (e.g., IP4 for IPv4 addresses)

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TCP monitor

TCP monitors attempt to open a connection to a host and port, and report whether the port is open, timeout, or error.

Configuration

Field	Type	Default	Notes
hosts	Array<{ type, host, port, timeout }>	one empty host row	At least one host required
tcpEval	string (JS function)	built-in default	Optional custom eval

Host fields:

Field	Type	Default	Notes
type	IP4 | IP6 | DOMAIN	IP4	Address type
host	string	—	Required
port	number	80	TCP port to probe
timeout	number	1000	Connection timeout in ms

Default eval behavior

• UP if every host result has status === "open"
• DOWN otherwise
• Latency = average connection latency across all hosts

The built-in eval function:

async function (arrayOfPings) {
    let latencyTotal = arrayOfPings.reduce((acc, ping) => {
        return acc + ping.latency;
    }, 0);

    let alive = arrayOfPings.reduce((acc, ping) => {
        return acc && ping.status === "open";
    }, true);

    return {
        status: alive ? 'UP' : 'DOWN',
        latency: latencyTotal / arrayOfPings.length,
    }
}

Custom eval contract

Your function receives arrayOfPings (TCP result objects) and must return { status, latency }.

Example

{
    "type": "TCP",
    "type_data": {
        "hosts": [
            { "type": "IP4", "host": "db.example.com", "port": 5432, "timeout": 2000 }
        ]
    }
}

Troubleshooting

• Timeout: the network path is blocked or the service is slow to accept connections
• Error: the host is wrong, the port is not listening, or DNS resolution failed
• Validation error: the type field must match the format of the address

---

DNS monitor

DNS monitors query a DNS record for a host and compare the returned values to your expected list.

Configuration

Field	Type	Default	Notes
host	string	—	Required — the domain to query
nameServer	string	""	Optional DNS resolver override
lookupRecord	string	A	Record type to look up (e.g. A, AAAA, CNAME, MX, TXT)
matchType	ANY | ALL	ANY	How to compare results to expected values
values	string[]	[]	Expected record values (at least one required)

Match behavior

matchType	Result
ANY	UP when at least one expected value is present in the DNS response
ALL	UP only when every expected value is present in the DNS response

Value normalization

Before comparison, both the DNS response values and your expected values are normalized:

• converted to lowercase
• trailing . removed
• whitespace trimmed

Example

Check A record

{
    "type": "DNS",
    "type_data": {
        "host": "example.com",
        "lookupRecord": "A",
        "matchType": "ANY",
        "values": ["93.184.216.34"]
    }
}

Troubleshooting

• Unexpected DOWN: copy the exact value from a manual dig query — normalization applies, so remove trailing dots
• No response: verify that the record type exists and that the resolver is reachable from Kener
• Partial mismatch with multiple IPs: use ANY for dynamic DNS setups where the response varies