Web Server Listen For When ERC20 Token Transferred

Question

Is it possible to have a web server listen or know when a transfer has been made on a particular ERC20 Token Contract?

From what I researched, we are not able to make a HTTP request inside the contract's transfer method.

Is there some way for an external web server to "watch" the blockchain for when those custom tokens are transferred?

Thanks

This is possible using javascript web3js and events – Badr Bellaj♦ Aug 17 '17 at 9:31 — Badr Bellaj♦, Aug 17 '17 at 9:31
Are you able to explain more? Any examples? – keweli Aug 17 '17 at 9:38 — keweli, Aug 17 '17 at 9:38

Thomas Clowes · Accepted Answer · 2017-08-17 11:52:26Z

0

As you can see in the token tutorial, at the end of the transfer method the following code is executed:

/* Notify anyone listening that this transfer took place */
Transfer(msg.sender, _to, _value);

This emits an Event.

You can 'listen' for emitted Events using web3.js for example.

answered Aug 17 '17 at 11:52

Thomas Clowes

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If this answer helped you, please mark it as correct. – Thomas Clowes Aug 17 '17 at 13:32

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