ICMP, TCP, and UDP
Choose a diagnostic transport and understand platform capabilities.
Open Configure Probe for a new or selected live target and choose Protocol. Each protocol measures qualifying diagnostic responses; none performs an application-level transaction such as fetching a web page.
ICMP
ICMP uses echo probes for the endpoint and TTL/hop-limit expiry responses for intermediate hops. It is the default protocol and does not require a destination port.
macOS uses the system traceroute / traceroute6 ICMP implementation for packet round-trip measurements. Its ICMP timeout must be at least 1 second. Windows uses the native .NET Ping implementation. On Windows, intermediate TTL-expiry RTT is an estimate that includes managed call overhead; endpoint echo RTT comes from the ping reply.
TCP
TCP monitors the configured destination port, initially 443. Choose the actual port you need to investigate.
A validated connection response establishes TCP reachability. Some validated reset responses establish that the host replied while the port is closed. A generic socket refusal or rejection without validated origin is not treated as a confirmed destination reply. Review the result details before interpreting a closed port as an available service.
TCP endpoint timing includes connection-call overhead. It does not establish HTTP, TLS, login, or other application-level health.
UDP
UDP sends a datagram to a fixed port or cycles sequentially through an inclusive port range. The remembered initial UDP port is 33434; the default range ending port is 33625.
A matching UDP reply or validated destination ICMP Port Unreachable response can establish destination reachability.
Reachability is not service availability
An ICMP Port Unreachable response confirms that the destination replied to the UDP diagnostic probe. It does not confirm that a UDP application is listening or working. An unanswered UDP probe also cannot establish that the host is down.
UDP ports can affect load balancing and routing. A range may reveal different paths from a single fixed port. Packet size includes IP and UDP headers, with a default total of 56 bytes. See probe configuration.
Platform capabilities
| Platform | ICMP | TCP and UDP |
|---|---|---|
| macOS | Native endpoint and hop probing | Hop receiver support; TCP depends on the bundled helper |
| Windows | Native endpoint and hop probing | Endpoint monitoring available; raw ICMP hop receiver can require explicit elevation |
Pngr tests local transport availability and shows warnings when hop discovery is unavailable. On Windows, an access-denied raw receiver leaves endpoint monitoring available. Pngr installs no driver or monitoring service and never automatically requests elevation.
If the macOS TCP helper is missing, TCP endpoint monitoring still works while intermediate-hop discovery is unavailable. Network filtering can suppress replies even when local capability checks succeed.