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Checkport

This is a simple application I made for NextcloudPi.

It checks if the port-forwarding has been done properly and the device is reachable from outside the network.

It does this by trying to open a TCP socket connection to port 80 & 443 on the client IP that is sending a HTTP GET request to the /check endpoint of the application.

Returns JSON response body with the following information:

  • § ip: Client IP
  • § format: valid | invalid | error
  • § type: IPv4 | IPv6
  • § 80: open | closed
  • § 443: open | closed

§ Clone the repository

git clone https://github.com/ZendaiOwl/checkport

§ Create a virtual environment with venv

python -m venv venv

§ Activate the virtual environment

source venv/bin/activate

§ Install sanic with

pip install -r ./requirements.txt

§ Run it locally

I've deployed this app on fly.io so I've changed the app's config for the client IP header to fly.io proxy's header name for the client IP.

It will fall back on the request IP if the proxy header is None, so it should work fine for development locally as is.

Run with

sanic server:app --dev -p 8080

If you omit -p 8080 it will default to port 8000 when running sanic with the --dev flag.

Ex. A GET request to the applications /check endpoint.

curl --silent https://localhost:8080/check

Receives the following response.

Note: The IP-address are examples in accordance with RFC3849 & RFC5737.

  • § IPv6
{
  "ip": "2001:DB8::C200:2B46",
  "format": "valid",
  "type": "IPv6",
  "80": "closed",
  "443": "closed"
}
  • § IPv4
{
  "ip": "192.0.2.12",
  "format": "valid",
  "type": "IPv4",
  "80": "closed",
  "443": "closed"
}

You can test it using netcat, start a listener on both or one of port 80 & 443.

You may need to allow TCP traffic if you have an active firewall blocking incoming traffic

sudo nc -l 127.0.0.1 80  # Netcat listens on 127.0.0.1 (localhost) Port 80
sudo nc -l 127.0.0.1 443 # Netcat listens on 127.0.0.1 (localhost) Port 443

Send a GET request with curl on localhost or 127.0.0.1

curl -s localhost:8080/80
# Output ↓
{"ip":"127.0.0.1","format":"valid","type":"IPv4","80":"open"}

curl -s localhost:8080/443
# Output ↓
{"ip":"127.0.0.1","format":"valid","type":"IPv4","443":"open"}

curl -s localhost:8080/check # 80 & 443
# Output ↓
{"ip":"127.0.0.1","format":"valid","type":"IPv4","80":"open","443":"open"}

I've used Sanic webserver and the Python Socket low-level library to reduce the data usage for each request as much as possible.

If you want to deploy one yourself as a Docker image you can build one using the Dockerfile, otherwise you need to install the dependencies in the requirements.txt file.

# $USERNAME: Username at the Docker Hub image registry
# $REPOSITORY: Repository at the Docker Hub image registry
# $IMAGE_TAG: The tag for the image
docker build . -t "$USERNAME/$REPOSITORY:$IMAGE_TAG"

Or if you want to use the one I've built

docker pull zendai/checkport:sanic
docker run --rm --detach --publish 8080:8080 zendai/checkport:sanic