Reticulum interface discovery location_cmd for Signal K

get_location.py

#!/bin/env python3
import urllib.request
import json
import sys

# Replace with your actual Signal K server address and port
# (e.g., http://localhost:3000/signalk/v1/api/vessels/self/navigation/position)
SIGNALK_URL = "http://192.168.2.105/signalk/v1/api/vessels/self/navigation/position"

def fetch_signalk_position(url):
    try:
        # 1. Fetch the JSON document
        req = urllib.request.Request(url, headers={'User-Agent': 'Mozilla/5.0'})
        with urllib.request.urlopen(req) as response:

            if response.status == 200:
                raw_data = response.read().decode('utf-8')

                # 2. Parse the JSON document
                parsed_data = json.loads(raw_data)

                # 3. Extract the position payload
                # Signal K REST API often nests the data inside a 'value' object.
                # If you queried the '.../position/value' endpoint directly, it won't be nested.
                # Using .get("value", parsed_data) safely handles both scenarios.
                position = parsed_data.get("value", parsed_data)

                lat = position.get("latitude")
                lon = position.get("longitude")

                # Altitude might not be present from all GPS sources, defaulting to 0.0
                alt = position.get("altitude", 0.0)

                # 4. Format and write the string to STDOUT
                if lat is not None and lon is not None:
                    formatted_string = f"{lat}, {lon}, {alt}\n"
                    sys.stdout.write(formatted_string)
                    sys.stdout.flush()
                else:
                    sys.stderr.write("Error: 'latitude' or 'longitude' not found in the response payload.\n")

            else:
                sys.stderr.write(f"Failed with HTTP Status: {response.status}\n")

    except urllib.error.URLError as e:
        sys.stderr.write(f"Connection Error: {e.reason}\n")
    except json.JSONDecodeError:
        sys.stderr.write("JSON Parse Error: The response from the server was not valid JSON.\n")
    except Exception as e:
        sys.stderr.write(f"An unexpected error occurred: {e}\n")

if __name__ == "__main__":
    fetch_signalk_position(SIGNALK_URL)