WebThing: Add

This is a WebThing to perform an addition of two numbers. Use it to add numbers in gateways which do not support adding two outputs.

Explanation

A + B = Y

Y is the sum of the modifiable properties A and B.

Property | Internal name | Type | Modifiable? | Description ---|---|---|---|--- A | a | number | yes | First summand B | b | number | yes | Second summand Y | y | number | no | The sum of A and B

Installation

Download the repository into a folder and install the dependencies. You may do this by running:

# Download the repository via git
git clone https://gitlab.com/webthings/webthing-add.git

# Install project dependencies
npm ci

Run

# Specify a port in Bash (Linux and Mac)
#export PORT=8000
# Specify a port in Batch (Windows)
#SET /A PORT=8000

npm start

This starts a web server on your machine. By default it starts on TCP port 8000. Determine your system’s local IP address and add the WebThing to your gateway.

Trouble shooting

It fails to start with Error: listen EADDRINUSE :::8000

You already have an instance of this project or another application running on the mentioned TCP port. On a computer a port cannot be assigned to two servers.
On Linux you can identify open TCP ports and the owner process with the command netstat -lnpt.

The server is not reachable from another computer

Ensure that the computers are on the same network. Test their connectivity with the ping command. If they are connected, the computer running the server might block the TCP port with its firewall.