@Read.Cash 4 November 2019

How to wait for the incoming or outgoing transactions on BCH network to the particular address So, you've implemented Bitcoin Cash in your site or app, now you need to react as soon as a user sends a transaction or gets an incoming transaction to his/her address. You could, of course listen to the entire BCH blockchain, like here: https://bitsocket.bch.sx/s, but that's pretty ineffective. Here's how to listen to a single address: Bitcoin Cash MainNet MainNet is better, because it has a few BitSocket servers. // These imports are not necessary in browser, only in npm // const btoa = require('btoa'); // const EventSource = require('eventsource'); function waitForTxMainnet(cashAddress) { return new Promise((resolve) => { const addr = cashAddress.split(':')[1]; const query = { "v": 3, "q": {"find": {$or: [{"out.e.a": addr}, {"in.e.a": addr}]}}, "r": { "f": ".[] | { id: .tx.h }" } }; const b64 = btoa(JSON.stringify(query)); const bitsocket = new EventSource('https://bitsocket.bch.sx/s/' + b64); bitsocket.onmessage = function (e) { // console.log(e); const data = JSON.parse(e.data); if(data.type === 'mempool') { bitsocket.close(); resolve(data.data.id); } } }); } // Usage: (async () => { const txid = await waitForTxMainnet('bitcoincash:qrg8ppy89pq9znsgws5e85x8xy5d3njvvus7825tev'); console.log(txid); })(); The `q` parameter is the query in BitSocket. `r.f` is the "output script" (just the transaction's hex representation). https://docs.planaria.network/#/query To use it call: `await waitForTxMainnet(cashAddress)` in your `async` function. This returns the actual transaction id. This uses `https://bitsocket.bch.sx/s/` BitSocket, but similarly `https://bitsocket.bitcoin.com/s/` is also available. Details of the transaction: https://rest.bitcoin.com/v2/transaction/details/499e4505967e1dd89cca239c99daff6b36ce19f4038c22759a6504d5e5ee2270 Balance of the address: https://rest.bitcoin.com/v2/address/details/bitcoincash:qrg8ppy89pq9znsgws5e85x8xy5d3njvvus7825tev Bitcoin Cash TestNet We haven't found any Socket servers watching Bitcoin Cash testnet, so the only way we've found is to watch UTXOs (unspent transaction outputs) for change: const axios = require('axios').default; async function waitForTxTestnet(cashAddress) { function sleep(ms) { return new Promise(resolve => setTimeout(resolve, ms)); } const url = `https://trest.bitcoin.com/v2/address/details/${cashAddress}`; const r = await axios.get(url); const txOriginal = r.data.transactions; while (true) { const r2 = await axios.get(url); const txNew = r2.data.transactions; if (JSON.stringify(txNew) !== JSON.stringify(txOriginal)) { const allNewTxes = txNew.filter(function (el) { return txOriginal.indexOf(el) < 0; }); return allNewTxes[0]; } await sleep(3000); } } // Usage: (async () => { const txid = await waitForTxTestnet('bchtest:qpfay8rvp96rrhefean4u97hn6tse5nu2s2wh95tkr'); console.log(txid); })(); It will poll rest.bitcoin.com every 3 seconds to see if UTXOs changed. It's not immediate, but good enough for testing. Just call `await waitForTxTestnet(cashAddress)` in your `async` function. Details of the transaction: https://trest.bitcoin.com/v2/transaction/details/d641d5b5d8864e74fa0f7367248670bcff3a9024597688134564b24c38b49c0b Balance of the address: https://trest.bitcoin.com/v2/address/details/bchtest:qrn808zezlasdgwp0ychx0npr2k0x446hudhkuzlep