### Gist: Add Inbound IPv4 Ports to iptables Configuration

#### Description:
This Bash script allows sysadmins and developers to easily add inbound IPv4 port rules to the `iptables` configuration of an Ubuntu server. Rather than using UFW, this script directly manipulates the `iptables` configuration, ensuring that new rules are inserted in the correct order to be effectively considered by the firewall.

#### Prerequisites:
- An Ubuntu server.
- Root or sudo access to the server.

#### Usage:
1. **Clone the Gist:**
   Download the script `add_port.sh` from the Gist and upload it to your server.

2. **Permission Assignment:**
   Ensure the script has execute permissions by running the following command:
   ```bash
   chmod +x add_port.sh
   ```
   
3. **Execute the Script:**
   Run the script with the desired port number as an argument using superuser privileges:
   ```bash
   sudo ./add_port.sh <port_number>
   ```
   Replace `<port_number>` with the actual port number you want to allow through the firewall.

#### Parameters:
- **`<port_number>`**: (Required) The port number you want to open in the firewall. Must be a valid port number (1-65535).

#### Notes:
- The script performs a basic validation of the port number but does not check if the port is already in use or already allowed through `iptables`.
- Always verify the new `iptables` rules after applying them and ensure connectivity to avoid unintentional lockouts.
- Additional security measures (e.g., IP whitelisting) might be needed for opened ports to mitigate potential risks.
- The script assumes that the SSH rule (port 22) is present in the `iptables` configuration file and inserts the new rule after it. Adjust the script as needed based on your specific `iptables` configuration.
- Please thoroughly test the script in a secure environment before using it in production to ensure it behaves as expected.

#### Disclaimer:
Use this script at your own risk. The author is not responsible for any network issues, lockouts, or security vulnerabilities that may arise from the use of this script.

#### Contribution:
Feel free to fork this Gist and contribute by submitting a Pull Request. Ensure that your code is clean and well-commented.