Web3 API doesn’t allow you to subscribe directly to a wallet’s incoming transactions, so to solve our particular problem, we have to use a different strategy. First, we subscribe to all pending transactions, then we filter them by the sender’s wallet address and certain other criteria.Web3.js allows us to talk directly to an Ethereum node via multiple protocols, including HTTP and WebSockets. For example, I use Rinkeby Testnet and nodes provided by Infura. However, you a free to use any other...