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I want to watch a set of Ethereum contracts and be notified (preferably by email) when a contact receives a payment to it.

I prefer me not to write my own software for this and not to install it on my own server, but programming suggestions are welcome.

  • are those your own contracts or just any contracts you want to watch ? – Cԃաԃ Dec 21 '18 at 6:02
  • @Cԃաԃ I created these smart contract myself, using my own software – porton Dec 21 '18 at 6:08
  • I wrote an answer for a setup you could use, I'm currently running this setup myself. – Cԃաԃ Dec 21 '18 at 6:26
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You could use the next setup.

1) in solidity inside of the payable function add event that will fire every time someone pays. for example : PaymentReceived

event PaymentReceived(address from, uint amount);
emit PaymentReceived(msg.sender, msg.value);

2) start a nodejs server with web3js and watch for the event PaymentReceived with web3js it will be something like this :

var ev = myContract.PaymentReceived({},{fromBlock:0, toBlock:'latest'});
ev.watch(function(error, result){
        if(!error){
                // send email here
        }else{

        }
});

3) you could use module like shelljs to run a script on linux to send email.

shell.exec('./sendEmailScript');

P.S. when watching for the event, you may want to use some sort of mechanism to check if you already send the notification email for a payment. Since every time you restart node application it will trigger send email script for every emit from solidity (because of this : {fromBlock:0, toBlock:'latest'}) I would save it a database, say mysql with tx as unique key, and send email only if it hasn't been send already.

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