OpenWarn-Proxy

-- OpenWarn-Proxy gathers civil protection alerts from the German office for civil protection at https://warnung.bund.de and proxies them to a websocket. Clients can open a websocket connection and provide a location as longitude/latitude. If an alert matching that location shows up (or is already known to the proxy), it is sent to the client.

Client messages are JSON encoded and look like this:

{
    "Latitude": 48.8345,
    "Longitude": 8.3819
}

The response is a JSON encoded array of alerts. To get an idea of how the response may look, take a look at the source for the alert messages at one of the following URLs:

- https://warnung.bund.de/bbk.mowas/gefahrendurchsagen.json
- https://warnung.bund.de/bbk.biwapp/warnmeldungen.json
- https://warnung.bund.de/bbk.dwd/unwetter.json
- https://warnung.bund.de/bbk.lhp/hochwassermeldungen.json

To run the proxy, simply run the binary like this:

./OpenWarn-Proxy -updateDelay=1m30s -socketPath=/coords -socketAddr=:8080

This will poll for updates ever one-and-a-half minutes and provide a websocket at path "/coords" on port 8080. To connect from a locally running browser, open its Javascript console and run the following:

ws = new WebSocket("ws://localhost:8080/coords");
ws.onmessage = (msg) => { console.log(msg.data) };
ws.onopen = (event) => {
	send(JSON.stringify({Latitude: 48.8345, Longitude: 8.3819}))
};

You will immediately get a list of active alerts for that location, and if a new one comes in, it will be provided to the websocket and the callback function will run again.