davis-wx

README

davis-wx

Real time consumption of weather data from Davis WeatherLink Live.

Table of Contents

• About
• Building
• Usage
• Websocket Protocol
• License

About

davis-wx is used to consume from a WeatherLink Live (WLL) unit located on a LAN (local area network). It takes advantage of Davis' live transmission protocol allowing for updates every 2.5 seconds. It also uses an adaptive protocol by only sending data when changes have been detected. This minimizes the amount of data usage while still keeping a fast end-to-end response time.

davis-wx captures live weather data from a WLL unit and pushes it to a Websocket server.

Building

davis-wx may be fetched using Go get:

go get github.com/thetannerryan/davis-wx

If you prefer to build the application manually, clone this repository and run go build -o davis-wx.

Usage

The command below shows the usage of davis-wx:

davis-wx --davis 172.16.0.2 --host websocket.example.com --endpoint /weather --passphrase mysecurepassphrase --secure

Parameters:

• davis: IP address or domain of WLL unit
• host: IP address or domain of receiving Websocket server
• endpoint: URL path/route to Websocket server
• passphrase: Websocket authentication passphrase
• secure: force websocket connection over TLS (WSS)

Running the command will connect this client to the Websocket server (e.g. wss://websocket.example.com/weather for example above) and begin uploading weather data as it is captured from the WLL unit.

Some operating systems may require root/admin privileges to open the UDP socket. If UDP errors are displayed in the program log, please ensure the program has appropriate permissions to open a Websocket.

Websocket Protocol

davis-wx does not come with a Websocket server. The Websocket server must implement a simple protocol:

1. Send a Websocket ping control message every 10 seconds.
2. The first message sent by davis-wx is the client passphrase. If the server implements authentication and the passphrase is incorrect, the server must disconnect the client (davis-wx client). If the server does not implement authentication, this first message may be ignored.
3. Every following message sent is a JSON weather report. The format of the report may be viewed here.
4. Set a client read deadline (recommended value of 30 seconds). A client (davis-wx client) must be disconnected if no messages are received by the server within the read deadline.

License

Copyright (c) 2020 Tanner Ryan. All rights reserved. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.

The Gorilla Websocket package is under a BSD 2-clause license. Cenk Alti's Go exponential backoff package is under an MIT license. Once again, all rights reserved.