blockchain: how to verify if a bitcoin address received a new transaction programmatically?

You can configure a bitcoin core node to observe new transactions and notify you about them.

This is a preferable solution, since you will not have to trust anyone to provide you with the correct information (what if they lie or are incorrect?), And you will retain your privacy (why bother with the addresses that you are interested in, to the API provider and to anyone else who listens to your connection?).

You can configure the command -walletnotify= in your bitcoin.conf file and write a bash script to alert you of the transaction in question, however you prefer (write to a log file, send an email alert, a light flashes, etc.).

For a slightly deeper tutorial on how to configure this, see this question: How do I use walletnotify?

Top-notch features of a multi-coin wallet

Have you ever wondered what makes a dynamic multi-crypto wallet? If you're right! The features that combine to develop a wallet make it stand out from the crowd.

http://blockchainhints.mystrikingly.com/blog/top-notch-features-of-a-multi-cryptocurrency-wallet

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bitcoin core: blockchain save destination folder

I will activate a full Bitcoin Core node on my PC. When selecting a custom folder in which to save the blockchain, I receive the error message:
"There was a fatal error. Bitcoin can no longer continue safely and it will close."
The only button I can press is "OK", after which the Bitcoin Core application crashes / closes and restarts, the same error appears again every time. Is it a mistake or is it something that developers want to not be able to change the blockchain save destination folder?
My operating system is Ubuntu 18.04, my version of Bitcoin Core is 0.19.0.1 (Snap).

Thank you.

json rpc: is it possible to skip blockchain data verification when using bitcoin core?

I just want to save my bandwidth

Running a node in pruned mode will not save you bandwidth during the initial download of the block (synchronization), you still need to download all the blocks and validate them, even if you do not store them in the long term (pruning reduces disk space requirements) . However, you can adjust your data load limits in the bitcoin.conf file.

Most RPC calls will work with a pruned node, although some will not. For a quick search of some examples, see:

https://github.com/bitcoin/bitcoin/blob/v0.11.0/doc/release-notes.md#block-file-pruning

https://github.com/bitcoin/bitcoin/blob/v0.12.0/doc/release-notes.md#wallet-pruning

ethereum – Execute smart contract on my own blockchain?

I developed a cryptography like bitcoin based on a blockchain using nodeJs, it is not using EVM, therefore, it uses the JavaScript interpreter.

In fact, I want to develop an automatic payment insurance system: the nodes in my private network, check if an airline flies late or not, for example, if a customer is expected to fly from Paris (departure at 02h00) to London ( arrival at 03h00), then at 03h10 some nodes will check if the cosutmer is really in London at the right time (03h00) obtaining data from this airline's web service, therefore, if there is a delay, then a transaction (pay to this client because there is a delay and the use of my own crypto) will be executed.

So my question is: can I develop a smart contract and import it into my own blockchain to do what I explain? If so, how can I do that?

blockchain – Multi-currency wallet (universal wallet)

I would like to create a multi-currency wallet like POC. I can currently make a wallet for Ethereum (like balance, tx and everything) but I would like to create it for others (like Bitcoin) as well.

I have examined the universal wallets available on the net, namely:

Ethos
Jaxx
Atomic
Trust

and I was thinking of doing something in that sense

I would like to get answers to some questions.

Just like using web3js for ETH, is there a way to do it for BTC? Same way like Infura, metamask etc etc for bitcoin exist or not?

Do I need to track which address generated by HD wallet is going to be used for which type of coin?
How will I add a custom ERC tokens in the wallet?
How will I combine multiple blockchains (Ethereum, bitcoin etc etc) to work together for my wallet?

I am looking for directions and resources to start somewhere. Any advice would be helpful.

Why do two different fully synchronized Bitcoin Core nodes differ in the size of the blockchain?

the size_on_disk printed on execution getblockchaininfo It is 1.2 GB smaller than other nodes that report at the same time / block.

txindex = 1

What could it be??
I asked other peers on Twitter to verify if someone else is experiencing the same and everyone has more data in their ledger than me. (https://twitter.com/bitdov/status/1231915231368163328)

Here is all the information printed with getblockchaininfo on my node:

{
  "chain": "main",
  "blocks": 618824,
  "headers": 618824,
  "bestblockhash": "0000000000000000000a1fb0ec42e380215bb58698a1321d2953ee5d1b7b                                                                                                                                                  685d",
  "difficulty": 15546745765529.37,
  "mediantime": 1582569829,
  "verificationprogress": 0.9999950821417113,
  "initialblockdownload": false,
  "chainwork": "00000000000000000000000000000000000000000cfea65b1b3c9262e87778b8                                                                                                                                                  ",
  "size_on_disk": 299006763199,
  "pruned": false,
  "softforks": {
    "bip34": {
      "type": "buried",
      "active": true,
      "height": 227931
    },
    "bip66": {
      "type": "buried",
      "active": true,
      "height": 363725
    },
    "bip65": {
      "type": "buried",
      "active": true,
      "height": 388381
    },
    "csv": {
      "type": "buried",
      "active": true,
      "height": 419328
    },
    "segwit": {
      "type": "buried",
      "active": true,
      "height": 481824
    }
  },
  "warnings": ""
}

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bitcoin core: how to create BTC raw transactions with 0 BTC Wallet and transmit them on the Blockchain network?

I think it's a scam.

To build a bitcoin transaction, you must have UTXO other than 0 and a public key. The invalid transaction would not be available in bitcoin core mempoool. So, to create it, you would have to have non-zero UTXO and pubkey.
There is no possibility that the software in the video is centralized, if the creators would use their own funds with non-zero UTXO, with zero fees, any miner could attack it through priority mining.

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