All Questions

UPDATED: I am trying to download source code of open source verified contract from Etherscan.io. Here is my procedure as directed by Ann. 1. Download CSV file of captioned contracts. 2. Write ...

I would like to save daily prices of about 3000 items (about 2mb in size) on a public blockchain, and I would like to create a DAPP to retrieve the data. I am considering saving the data on Ethereum. ...

I've been playing with this over the past weekend and it seems impossible, I guess since it's considered a big security issue if it was possible. Example to illustrate what I am trying to achieve: ...

ethereum-wallet-xxx.jsonfile exists when purchasing genesis. I do not know if I set a password. Is this possible to restore? There are encseed, bkp, ethaddr, btcaddr, and email file formats.

I am requesting test ether from a Ropsten faucet, but it is showing an error. Please help me to resolve this error.

I am trying to understand Chainlink, and I am running into a wall. I found this tutorial, which explains how I can create a job spec using JSON. The tutorial explains that you can specify the url, ...

Python code: from web3 import Web3 import json web = "http://10.0.141.114:8545" web3 = Web3(Web3.HTTPProvider(web)) abi=json.loads('[ { "constant": false, "inputs": [ { "name": "_cad_number", "type":...

I have deployed my contract locally into Ganache (GUI) and then send/call lot of transactions. After these transactions, now I want to check the current status of all state variables. Is there any way/...

I am using geth to sync up with the Rinkeby testnet using the command: geth --rinkeby --syncmode "fast". First it downloaded the blocks, then account states, and now new chain segments are being ...

How can I accomplish something like this: accept ether, set owner or anything and then return 1, throw...just return This doesn't seem to work despite crossing through functions and using if ...

What kind of node synchronization should I choose to work with a centralized exchange? Is there enough quick synchronization, or is full synchronization necessary?

Given the following example: function x(address receiver) public { receiver.call.value(msg.value)(); } Am I correct that receiver can be any address but msg.value cannot be controlled via ...

Im doing the tutorial at https://github.com/ConsenSys-Academy/proof-of-existence-exercise and running into the following error: $ truffle console truffle(development)> var poe = await ...

I am making my project of BlockChain subject. I am having a problem with deploying smart contracts. Can anyone help me with this error I have tried everything I could but still failed to resolve this ...

I have been studying block chain for a while, and I came to know that decentralisation of data is its greatest pros. From my understanding, if block chain is massively adopted in the future, we will ...

I want to query all transfers regarding a contract with Nethereum. This means, in the end I want to have all transactions, so that I can print a statement of account. I suppose with the web3.js ...

I have a truffle project, if I migrate it onto ganache-cli and then interact with my contract (via Metamask) it works great. But if I try and do the exact same thing using ganahe-gui the contract ...

When I deploy my truffle smart contract on test networks like Ropsten and Kovan, can I interact with it using multiple PCs at once simultaneously? And will the data updated from one PC be visible on ...

The question is about the node, is the node functionality enough in fast synchronization for the functioning of a centralized exchange? Or is it necessary to download a node in full synchronization?

In other words: If contract B is called by contract A: B: function externalcall() public { //msg.sender is contract A... msg.sender.call.value(0); } Then assuming msg.sender.call above calls back ...

What server configuration is needed to raise a node? And will there be enough nodes in fast synchronization mode for the exchange, or is full synchronization necessary?

I have read about smart contracts and I am left with some doubts. Every invocation of a function in smart contract is a transaction which costs some ether.A miner chooses a smart contract on ...

I'm just studying about Ethereum, ENS and and and.. Actually I try to compute an ENS .eth Name to a hash. In https://app.ens.domains/name I baught a ENS .eth Name with the Ropsten Testnetwork. Now I ...

For instance delegatecall to the same address works: function callTheOtherContract() public { require(address(this).delegatecall(bytes4(keccak256("callMe()")))); } event CallMe(...

Has this mechanism for selecting validators been proposed and/or implemented in any distributed ledgers? Validators pre-commit hash chains of length w. When creating a block, validators commit the ...

I want to create a payable function that acts similarly to onlyowner modifier, or: function owner() public payable{ if(msg.sender != owner) { balances[owner] += msg.value; revert(); } } What ...

I want to download all contracts (open source code) from etherscan.io using Web3js. Etherscan gives only the list of such verified open source contract with txHash, name, and their addresses. Is there ...

I've been learning about interacting with smart contracts through Android and the Web3j framework but have run into an issue. I'm trying to mint an ERC721 token and send it to an address but it doesn'...

How do I get the msg.sender of the user who called randomNumber() in the __callback? pragma solidity ^0.5.11; import "github.com/provable-things/ethereum-api/provableAPI_0.4.25.sol"; contract ...

I have setup a private Ethereum node using the following configuration for the genesis block: { "config": { "chainId": 143, "homesteadBlock": 0, "eip150Block": 0, "eip155Block": 0,...

I have created two contracts A and B as follow: Contract A: pragma solidity 0.4.25; contract A{ // uint public X ; event MyName(address _from, address sender); function checkMe(uint val)...

I'm considering different designs to implement "configuration options" with Ethereum. The design should allow me to define arbitrary (= number and type) options, quick access to a list of options, ...

I have problem with invalid response to ethereum from BE NodeJS app. I got error like: Error: Invalid JSON RPC response: "" Below I'd attached my simple code for testing connection. const Web3 = ...

I have downloaded contracts with their abi and json. I have to deploy them. when i extract bytecode from downloaded files and then assign it to my data variable to deploy contract whic gives following ...

when doing e.g. a blockByNumber rpc request I am getting a result like this from parity: https://gist.github.com/ligi/fbc7061d93f087cf0eb0f4db83d1fced what is puzzling me that some transactions have: ...

Since the ratio of all possible digits (please correct my math if I am wrong) of a public key versus private is: 1/79228162514264337593543950336 for public (40^16): 1 461 501 637 330 902 918 203 684 ...

There is a contract with a betting function that calculates a random number and send you back a reward if winning. The betting function looks like: function bet() public payable { if ((...

Is there any reliable source for hourly data for Ethereum dating back to 2017? The poloniex API only provides me with daily data - https://poloniex.com/public?command=returnChartData&currencyPair=...

I need to create something like ethernodes.org or etherscan.io/nodetracker. First of all, I tried to implement Discovery Protocol by own, but after couple of minutes I realized that specs are too hard ...

I am getting this error when I try to add the truffle-config file to my project in ganache. What to do?

In the following article (LINK) we read: "despite the fact that at the time of this writing a new block is produced approximately every 10–20 seconds the average time it actually takes for a ...

The definition of web3.eth.Contract.transactionconfirmationblocks is here. But I don't quite understand the meaning. The default value is 24, does it mean a transaction will not be confirmed (i.e. the ...

How to configure a node and connect it to a browser so that I can perform erc20 token transactions on my site between users?

When I try to excute the deposit function it shows Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? execution ...

How can I interact with the smart contract on ganache from my express app using Web3.js Any Tutorials?

I have a erc-20 token in the ropsten testnet and i am using my metamask for admin my token, and i just want to recieve a notification via sms, to take screenshot, whatsapp or another way frendly user, ...

This is not a duplicate question. The other one doesn't answer the problem in any way. Can anyone explain to me why do I get No Events where emmited when running truffle test? Ganache is listening in ...

I have activated watching events with Contract.events.events_name(filter, lastBlock), now I need to stop watching this event. I can't find the command in web3 docs. I'm using Web3 version: 1.2.1. How ...

I want to retrieve the total number of an erc 721 token's transfers/ transactions. I couldn't scrape the transfers value from etherscan as well e.g. given here https://etherscan.io/token/...

gyp WARN install got an error, rolling back install gyp WARN install got an error, rolling back install gyp ERR! configure error gyp ERR! stack Error: EACCES: permission denied, mkdir '/usr/lib/...