Your First TCP Monitor

By the end of this guide, you’ll have a TCP monitor verifying that your service is accepting connections on a specific port.

Prerequisites

DevHelm CLI installed or an API token for REST calls
An API token set as DEVHELM_API_TOKEN — see Authentication
A host and port that accepts TCP connections

Create the monitor

Create the TCP monitor

devhelm monitors create \
  --name "Database Port" \
  --type TCP \
  --url db.example.com \
  --port 5432 \
  --frequency 60 \
  --regions us-east

version: "1"
monitors:
  - name: Database Port
    type: TCP
    config:
      host: db.example.com
      port: 5432
      timeoutMs: 5000
    frequencySeconds: 60
    regions:
      - us-east

curl -X POST https://api.devhelm.io/api/v1/monitors \
  -H "Authorization: Bearer $DEVHELM_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Database Port",
    "type": "TCP",
    "config": {
      "host": "db.example.com",
      "port": 5432,
      "timeoutMs": 5000
    },
    "frequencySeconds": 60,
    "regions": ["us-east"]
  }'

Verify it's running

devhelm monitors list --type TCP
devhelm monitors get <monitor-id>

Check results

Results show whether the TCP connection was established and the connection time in milliseconds.

devhelm monitors checks <monitor-id> --limit 5

Add assertions

monitors:
  - name: Database Port
    type: TCP
    config:
      host: db.example.com
      port: 5432
    frequencySeconds: 60
    regions:
      - us-east
    assertions:
      - config:
          type: tcp_connects
        severity: fail
      - config:
          type: response_time
          thresholdMs: 1000
        severity: warn

Available TCP assertions:

Type	What it checks
`tcp_connects`	Connection is established within the timeout
`response_time`	Connection completes within a threshold
`tcp_banner`	The server’s initial response matches an expected pattern

For details, see TCP configuration.

Common use cases

Database connectivity

Monitor PostgreSQL (5432), MySQL (3306), Redis (6379), or any database port to detect connection issues before they affect your application.

Internal service ports

Verify that microservices are accepting connections on their expected ports — useful for service mesh health checks.

SMTP/mail servers

Check that your mail server is accepting connections on port 25, 465, or 587.

Next steps

TCP monitor reference

Full TCP configuration and assertion details.

First alert

Get notified when the TCP connection fails.

Monitors guide

Configure all six monitor types.

Overview

Getting Started

Monitoring Guides

Alerting Guides

Incident Guides

Status Data Guides

Monitoring as Code Guides

Your First TCP Monitor

Create the monitor

Add assertions

Common use cases

Next steps

TCP monitor reference

First alert

Monitors guide

​Create the monitor

​Add assertions

​Common use cases

​Next steps

TCP monitor reference

First alert

Monitors guide

Create the monitor

Add assertions

Common use cases

Next steps