Check network-port-tcp

Overview

Checks whether a TCP network port is reachable by attempting to establish a connection. Useful for monitoring service availability from the network perspective.

Important Notes:

  • This check works with TCP connections only. UDP port responses depend on the target application (e.g. DNS or OpenVPN) and are not standardized like TCP.

Data Collection:

  • Attempts a TCP socket connection to the specified host and port

  • Supports both IPv4 (tcp) and IPv6 (tcp6) via the --type parameter

Fact Sheet

Fact

Value

Check Plugin Download

https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/network-port-tcp

Nagios/Icinga Check Name

check_network_port_tcp

Check Interval Recommendation

Every minute

Can be called without parameters

Yes

Runs on

Cross-platform

Compiled for Windows

Yes

Help

usage: network-port-tcp [-h] [-V] [-H HOSTNAME] [-p PORT]
                        [--portname PORTNAME] [--severity {warn,crit}]
                        [-t TIMEOUT] [--type {tcp,tcp6}]

Checks whether a TCP network port is reachable by attempting to establish a
connection. Measures and reports the connection time. Useful for monitoring
service availability from the network perspective. Alerts if the port is
unreachable or the connection time exceeds the configured thresholds.

options:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -H, --hostname HOSTNAME
                        Host or IP address to check. Default: localhost
  -p, --port PORT       TCP port number to check. Default: 22
  --portname PORTNAME   Human-readable display name for the port in the output
                        message. Example: `--portname https`.
  --severity {warn,crit}
                        Severity for alerting. Default: warn
  -t, --timeout TIMEOUT
                        Network timeout in seconds. Default: 2
  --type {tcp,tcp6}     Connection type, "tcp" for IPv4 or "tcp6" for IPv6.
                        Default: tcp

Usage Examples

./network-port-tcp --hostname www.linuxfabrik.ch --port 443 --portname https --timeout 1.3 --severity warn

Output:

www.linuxfabrik.ch:https/tcp is reachable.

States

  • OK if the port is reachable.

  • WARN (default) or CRIT (via --severity) if the port is unreachable.

  • UNKNOWN if the connection cannot be initiated (e.g. DNS resolution failure).

Perfdata / Metrics

There is no perfdata.

Credits, License