> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/dotandev/envcheck/llms.txt
> Use this file to discover all available pages before exploring further.

# Port Availability

> Check that required ports are available

## Overview

The `ports` section validates that specific network ports are available for use. This prevents conflicts when your application tries to bind to ports already in use by other services.

## Configuration

The `ports` field is a simple array of port numbers (src/config.rs:14):

<ParamField path="ports" type="array<number>" default="[]">
  List of port numbers to check for availability. Each port should be a number between 1 and 65535.
</ParamField>

## Format

Ports are specified as a simple YAML array:

```yaml theme={null}
ports:
  - 3000
  - 5432
  - 8080
```

## Examples

### Single Port

Check that a single port is available:

```yaml theme={null}
version: "1"

ports:
  - 3000
```

### Multiple Ports

Check multiple ports used by your application and services:

```yaml theme={null}
version: "1"

ports:
  - 3000  # Application server
  - 5432  # PostgreSQL
  - 6379  # Redis
  - 8080  # Development proxy
```

### With Comments

YAML comments help document which service uses each port:

```yaml theme={null}
ports:
  - 3000  # Next.js dev server
  - 5432  # PostgreSQL database
  - 6379  # Redis cache
  - 9200  # Elasticsearch
  - 5672  # RabbitMQ
```

## Real-World Examples

<CodeGroup>
  ```yaml Node.js Project theme={null}
  version: "1"

  tools:
    - name: node
      version: ">=18.0.0"
      required: true

  ports:
    - 3000
    - 5432

  files:
    - path: package.json
      required: true
  ```

  ```yaml Django Project theme={null}
  version: "1"

  tools:
    - name: python
      version: ">=3.9.0"
      required: true

  ports:
    - 8000  # Default Django dev server port

  files:
    - path: manage.py
      required: true
  ```

  ```yaml Rails Project theme={null}
  version: "1"

  tools:
    - name: ruby
      version: ">=3.0.0"
      required: true

  ports:
    - 3000

  files:
    - path: Gemfile
      required: true
  ```
</CodeGroup>

## Common Port Numbers

Here are commonly used port numbers for development:

| Port  | Service                           |
| ----- | --------------------------------- |
| 3000  | Node.js/Next.js/Rails dev servers |
| 3001  | Alternative Node.js port          |
| 4200  | Angular dev server                |
| 5000  | Flask default port                |
| 5173  | Vite dev server                   |
| 5432  | PostgreSQL                        |
| 6379  | Redis                             |
| 8000  | Django dev server                 |
| 8080  | Common HTTP alternative           |
| 8888  | Jupyter Notebook                  |
| 9200  | Elasticsearch                     |
| 27017 | MongoDB                           |

## Validation Behavior

Port checks verify that ports are **available** (not in use). Validation will fail if:

* A port is already bound by another process
* The port number is invalid (\< 1 or > 65535)
* Insufficient permissions to check the port (typically ports \< 1024 require elevated privileges)

<Warning>
  Port availability checks verify that ports are **not in use**. If a required service should already be running on a port, use [network checks](/configuration/network) instead to verify connectivity.
</Warning>

<Tip>
  Port checks are particularly useful in development environments where multiple projects or services might conflict. Run envcheck before starting your development server to catch port conflicts early.
</Tip>

## No Port Checks

If your project doesn't need to validate port availability, simply omit the `ports` section entirely:

```yaml theme={null}
version: "1"

tools:
  - name: go
    version: ">=1.18.0"
    required: true

files:
  - path: go.mod
    required: true
```

From src/config.rs:14, the `ports` field defaults to an empty array when not specified.