upd: monitoring of network connection

This is a small utility built as a single binary for easy deployment to monitor internet connections and reboot appropriate networking equipment if the connection is down.

It works by:

• Running HTTP, TCP or DNS checks on a regular basis.
• If all checks fail, runs a specified command on a regular basis until the connection is back up.

Installation

Download the latest release and extract the upd or upd.exe binary.

Help

upd -h and upd.exe -h will show:

NAME:
   upd - Tool to monitor if the network connection is up.

USAGE:
   upd [global options] command [command options]

COMMANDS:
   help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --config value, -c value  use the specified TOML configuration file (default: ".upd.toml")
   --debug, -d               display debugging output in the console (default: false)
   --help, -h                show help
   --version, -v             print the version

Configuration

Configuration by default is located in .upd.toml in the working directory.

See upd.toml for a complete, runnable example. Values can reference environment variables with ${VAR} syntax, e.g.:

[checks.every]
normal = "${UPD_NORMAL_CHECK}"
down = "${UPD_DOWN_CHECK}"

Probe-stat bucket granularity per report period is also tunable: each report period is split into at least min buckets (default 100), and a single bucket never aggregates more than maxSpan (default 30m):

[stats.buckets]
min = 100
maxSpan = "30m"

Status

In the configuration, stats can be used to capture statistics that are made available via a web interface at http://<ip>:42080/stats.json.

The sample configuration above will provide data looking like this:

{
  "isUp": true,
  "reports": [
    {
      "period": "10s",
      "availability": "100.00 %",
      "downTime": "0s",
      "totalProbes": 1,
      "failedProbes": 0,
      "failureRate": "0.00 %"
    },
    {
      "period": "15m",
      "availability": "100.00 %",
      "downTime": "0s",
      "totalProbes": 15,
      "failedProbes": 0,
      "failureRate": "0.00 %"
    },
    {
      "period": "1h",
      "availability": "100.00 %",
      "downTime": "0s",
      "totalProbes": 60,
      "failedProbes": 0,
      "failureRate": "0.00 %"
    },
    {
      "period": "24h",
      "coverage": "12h33m23s",
      "availability": "100.00 %",
      "downTime": "0s",
      "totalProbes": 753,
      "failedProbes": 0,
      "failureRate": "0.00 %"
    },
    {
      "period": "168h",
      "coverage": "12h33m23s",
      "availability": "100.00 %",
      "downTime": "0s",
      "totalProbes": 753,
      "failedProbes": 0,
      "failureRate": "0.00 %"
    }
  ],
  "loop": {
    "lastSuccess": "11s",
    "nextCheck": "49s",
    "interval": "1m",
    "timeSinceLastUpdate": "11s",
    "totalChecksRun": 753
  },
  "updUptime": "12h33m23s",
  "updVersion": "4.4.0",
  "generatedAt": "2026-06-09T07:37:00.70887063-05:00"
}