Start the server process in one terminal:
node server
Start the operator process in one or more terminal. It will produce random messages, with buy or sale products:
node operator
Start the subscriber process in one or more terminal. Examples:
node subscriber
node subscriber -o buy
node subscriber -o sale
node subscriber -p wheat
node subscriber -p wheat -o buy
The -p or --product flag indicates the product to listen, ie wheat.
The -o or --operation flag indicates the operation to listen: buy or sale.