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Questions tagged [blockchain]

The Ethereum blockchain is a distributed database based on the Ethereum whitepaper specification and stores both the full transaction list and the most recent state.

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Source file compile error

... Source file requires different compiler version (current compiler is 0.8.2+commit.661d1103.Emscripten.clang) - note that nightly builds are considered to be strictly less than the released version ...
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org.web3j.protocol.exceptions.ClientConnectionException: Invalid response received: okhttp3.internal.http.RealResponseBody

Environment Android Studio Infura – Rinkeby test network Web3J Metamask Rinkeby.etherscan.io I am trying to build an Android app to read and write smart contract by following the medium article: ...
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rafthttp: failed to find member 1 in cluster 1000 -quorum -raft consensus

Firstly, I have created a node in quorum private blockchain and initiated genesis to create blockchain using geth and bootnode . Then, I run the node and it is running blockchain. Later, I tried to ...
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clone pancakeswap but it's show error Unhandled Rejection (Error)

I clone pancakeswap-frontend. when run I got above error. But I can't solve this problem. Unhandled Rejection (Error): invalid address (argument="address", value=undefined, code=...
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What's the difference between Binance ERC20 and Coinbase ERC20 …?

As a newbie I made a mistake whilst transferring btc to from Binance and Coinbase. My mistake was I didn't check the receive address with Coinbase and it defaults to eth and I wanted to send btc to ...
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24 views

From what source does etherscan.io aggregate and broadcast data that appears on the blockchain ledger?

as blocks are hashed together as transactions pile up and are broadcasted on the Ethereum blockchain, how exactly does the website etherscan.io in turn publish and broadcast all that information in ...
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104 views

How to validate a transaction from any block in Blockchain

Given that we have a Blockchain with smart contracts. We have end users operating the platform for some time. Now one user wants to verify the claim of a transaction. Example, I have to prove that ...
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597 views

How to convert ERC crypto art NFTs into a Cardano NFT?

This is being asked two days before native tokens and multi-asset support hits the Cardano blockchain, but, given that Cardano has created an ERC-20 token converter that converts ERC-20 tokens to ...
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11 views

Is there any way to conduct multilateral netting on a DLT platform?

Multilateral Netting is generally used as a method to counter high liquidity requirement for the participating members. We always use a central clearing house/central counterparty who does this ...
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95 views

how to create a smart contract that uses ERC20 as way of payment?

im creating a smart contract that will receive and automatically redistribute erc20 tokens! how can i implement that in solidity? i've tried a couple of codes examples but nothing have worked so far! ...
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1answer
75 views

How to reduce time for block confirmation in the Ethereum blockchain and also time to listen to logs emitted?

I am designing an application in which I am emitting logs through transactions in the Ethereum blockchain. I also created an event listener to listen to the new logs emitted. But I want time from ...
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26 views

How to use promises with drizzle/vue-plugin

I'm trying to implement a blockchain based app. I'm using Drizzle Vue plugin to interact with the methods in smart contracts. However, I stumbled across the following issue. After executing the ...
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31 views

Please help with Parsing Expected ',' but got ';'

I have looked far and wide for a solution and have read solidity documentation. Please help me find the parsing error in the code. Thanks in advance. var KiwiCoinSale = artifacts.require('KiwiCoinSale'...
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349 views

Using Phoenix Miner - Noob Question

I am using Phoenix Miner - Ran it for around 8 to 10 hours as a trial - I setup my Public Wallet ID as My wallet ID, I have yet to see anything pending into my account - I am wondering If I am missing ...
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55 views

Invalid implicit conversion from rational_const 5 / 2 to uint256 requested

I have the following code snippet inside my contract: plans[1100] = Plan(7, 3); plans[1101] = Plan(7, 2.5); plans[1102] = Plan(15, 4); plans[1103] = Plan(30, 6); plans[1104] = Plan(30, 5); When I try ...
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18 views

Find ETH address with amount range (Query Big Data)

I'm trying to run a query similar to this: https://medium.com/google-cloud/how-to-query-balances-for-all-ethereum-addresses-in-bigquery-fb594e4034a7 But I would like to find ETH address: Ending with ....
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31 views

Problem with old Xeth wallet syncing up

I've got some ETH on an old XETH wallet from 5 years or so and I've never been able to retrieve it. The ETH doesn't show up in the wallet and the sync bar is completely blank. Based on another ...
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26 views

Get balance in fast node by Geth

Is it possible to get account Balance in fast node with Geth ? and what is the size of fast node currently?
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33 views

scheduling of smart contract functions

I am reading the alarm clock documentation http://docs.ethereum-alarm-clock.com/en/latest/ but there are things I don't understand. I have a dapp where the smart contract has different functions. For ...
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105 views

Non ERC 20 coin sent by mistake to MyEtherWallet (MEW)

Newbie here - apologies for anything inappropriate and lack of tech expertise. I made a dumb mistake and sent some THETA tokens to a MEW Ether address. My bad - I had not realised that THETA had moved ...
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1answer
40 views

If I don't use metamask who manages the private key and the incoming or outgoing ether?

I want to build a dapp without using metamask but web3.js and a node (geth / parity). So if I use this second method what happens when ethere needs to be sent to an account?
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1answer
112 views

Attempting to transfer erc20 elrond to elrond gold in trust wallet - error insufficient funds

Does anyone have a step by step guide to transfer my 7566 elrond to elrond gold? My elrond is in Trust Wallet and tried to send to my elrond gold wallet but network said I have insufficient funds and ...
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261 views

Error: VM Exception while processing transaction: revert UniswapV2: LOCKED

I am using this repo to begin testing UniSwap flash swap contracts. I've installed all dependencies correctly and cleanly. The project uses ganache-cli, hardhat buidler, and yarn in the terminal and I ...
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9 views

interact with a contract deployed by another account

How do I send transactions, subscribe to events and call methods from a contract already deployed on the blockchain? (in web3.js)
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Is it possible to access an already deployed smart contract without using metamask?

Suppose a user wants to access a contract on the blockchain hat was distributed by a company. Can it do this without the use of metamask? If so, how?
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19 views

Is the interaction with the smart contract safe?

I am working with ethereum and I have a doubt. In a real case, can a user interact directly with a smart contract? Are there no dangers? For example: a user wants to book a trip. What happens in these ...
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17 views

Should I run POW or POS for local Transactions?

Since prof of Stake is here, and proof of work is in decline, I am trying to figure the best corse of action. I need a local node, Geth node, and I need to be able to post transactions and retrieve ...
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2answers
52 views

how to set a require for a string to not be null

I want to write a require condition for string that string variable could not be null. How to write because string is not taking the != operator function createOrder(address _seller, string memory ...
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1answer
41 views

How to send ether from sender account to a given account

I am new to solidity and trying to develop a small smart contract. I want to send ether from the sender account to a given account. But I always get this error "VM error: revert. revert The ...
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14 views

intercation with smart contract

I am working on a dapp based on hotel bookings. I have a refund function in my smart contract. The smart contract can receive transactions from a single EOA of a component (contract manager) in the ...
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24 views

Oracle service and oracle smart contract

I read this article https://medium.com/@robinagist/building-an-ethereum-oracle-with-web3-js-1-0-1272b59cfc31 but there are some things I didn't understand. Does the oracle need a node (like geth or ...
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90 views

Run dapp in mobile metamask browser

I am having a dapp which is working perfectly in web browser using metamask wallet.Now I want to test my dapp in mobile browser using metamask mobile wallet. I tried to make transactions in BC using ...
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58 views

What is the theoretical average latency of data transmission?

I concluded a pretty simple test to measure some latencies. I connected to two providers (Infura and Quiknode) with Web3.js and subscribed to new block headers. Then I compared the time of arrival and ...
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27 views

differences in terms of api supported by full node vs light node

Are there any differences on the API supported by full node vs light node in Ethereum?
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1answer
23 views

In a dapp application who listens to events?

In a dapp application who listens to events? the geth node or my node.js component (backend component? How can I implement the listen function in web3.js?
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219 views

How to solve this error: “Cannot read property 'address' of undefined”?

ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'address' of undefined TypeError: Cannot read property 'address' of undefined This is my code that uses web3.js: public getContract(...
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1answer
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How can I create a similar application to YouTube on Blockchain? What is the cost of it?

How can I create a similar application to YouTube on Blockchain or as a smart contract? What is the cost of it?. I am keen on picking it up as a project. Thank you!
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13 views

How do I use in3 (Incubed) for Bash to view ethereum records for a given address?

I want to be able to query an ethereum contract address that I know is valid with the in3 module in bash. I have installed Incubed (in3) for bash), and I have used this documentation to try to query ...
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2answers
18 views

can we create our own cryptography system and use it with ethereum or hyperledger fabric frameworks?

i have a project where we have to build a fuzzy encryption for biomedical data like DNA and use it on blockchain for storage. So is it possible to create our own cryptography scheme on Ethereum and ...
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1answer
454 views

Uniswap fork: remove liquidity error

I am trying to fork uniswap. And I have a problem when liquidity is removed. Problem in UniswapERC20. I don't know what's wrong. Step by step (repeatedly for Rinkeby and Ropsten): Copy Uniswap ...
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40 views

“Getting AGE/TIMESTAMP of a Pending Transaction from a Transaction Checker”

Can I get TIMESTAMP of a pending transaction as soon as it's added to etherscan.io recent transactions list? I'm using GETH and WEB3 for a transaction checker and it's fetching me recent pending ...
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41 views

Fork Ethereum (geth source code)

I wanted to Fork geth source code to create my own currency like ethereum but changing the currency name. I want it to be able to carry smart contracts also that's why I am not forking bitcoin. Is ...
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20 views

When is the transaction mined?

I'm working on an ethereum blockchain project where people want to make reservations in a city. My backend sends a transaction to the smart contract with the user id, city and other data. The smart ...
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65 views

I have a problem with the transfer of ownership by a smart contract

I have a smart contract. I own, it belongs to my wallet. I am trying to implement a function to transfer the OWNERSHIP of this smart contract to another wallet. I have two solutions, but for some ...
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17 views

Issue with Solidity Payable function?

I get error when I try to call this function AvailableEnergyAdvert with energy_produced greater value > 1. pragma solidity ^0.6.0; import "https://github.com/OpenZeppelin/openzeppelin-...
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How do I pass a dictionary for the in3_registry value for the Incubed Python API?

I am using Python 3. I have installed the in3 (Incubed) Python module. I want to invoke the ClientConfig of the in3 Python API in a specific way. There is an in3_registry argument that is part of ...
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28 views

How to get all transactions in ganache-cli that have not been mined yet?

Considering a scenario in ganache where a block is mined every 200 seconds ganache-cli --blockTime 200 how can I get the all the transactions that have been sent but not yet mined?
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62 views

Will OmiseGO (OMG) become redundant when Ethereum migrates to Proof of Stake?

When Ethereum migrates to "Proof of Stake" to validate the transactions. Will OmiseGO (OMG) lose its value ? as scalability issues in Ethereum would be resolved after the migration and I am ...
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40 views

Trying to be a validator in blockchain but I have got the error : Mining aborted due to sync

I try to run blockchain in local to be a validator with this command : geth --config ./config.toml --datadir ./node -unlock {your-validator-address} --password password.txt --mine --allow-insecure-...
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1answer
27 views

Storing multiple values in one key mapping dynamically

I am making a blockchain project using solidity which requires storing various objectIDs corresponding to a personId. The person can add and remove objects and we cannot hard-code the number of ...

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