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

# Ports and firewalls on your VPS

> Find out how ports work on an EDBB VPS. Check application listeners, allow required traffic in your firewall and understand the outbound SMTP exception.

EDBB does not normally require you to ask support to open a TCP or UDP port. Your application must listen on the required port, and your operating system's firewall must allow the connection.

<Note>
  Outbound TCP port 25 has separate [SMTP limits and abuse controls](/faq/port-25-smtp-rate-limit-policy). Protective restrictions may also apply during attacks or abuse incidents. Inbound port 25 is unrestricted by the SMTP policy.
</Note>

## Check that your application is listening

<Tabs>
  <Tab title="Linux">
    ```bash theme={"system"}
    sudo ss -lntup
    ```

    Find the required port and process. An application bound only to `127.0.0.1` or `::1` cannot accept direct connections from outside the VPS.
  </Tab>

  <Tab title="Windows">
    Open PowerShell:

    ```powershell theme={"system"}
    Get-NetTCPConnection -State Listen
    Get-NetUDPEndpoint
    ```

    Match the local port and address to your application's configuration.
  </Tab>
</Tabs>

## Allow the required connection

Check the firewall used by your system: UFW, nftables, firewalld or Windows Defender Firewall. Open only the required protocol and port, and restrict administrative access to trusted source addresses where possible.

For Debian or Ubuntu with UFW, follow the [UFW guide](/advanced-setup-guides/ufw-firewall). Keep the [VNC console](/vps-management/enable-vnc-server) open before changing rules that could block your own access.

## Test from another computer

For a TCP service, replace the example IP and port with yours:

```bash theme={"system"}
nc -vz -w 5 192.0.2.10 443
```

On Windows, use:

```powershell theme={"system"}
Test-NetConnection -ComputerName 192.0.2.10 -Port 443
```

These tests check TCP connectivity, not whether the application works correctly. For UDP, use the application's own client or a protocol-specific test; a TCP test cannot establish whether a UDP service is reachable.

If the service works from one network but not another, check client firewalls, ISP restrictions and [country reachability](/faq/ip-addresses/country-reachability). For a server that is entirely unreachable, start with [VPS not reachable](/faq/ip-addresses/network-is-down).