All Questions

Filter by
Sorted by
Tagged with
0
votes
0answers
26 views

Error: Cross origin null forbidden : ---Problem in downloading Open source contracts from Etherscan.io

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 ...
0
votes
0answers
19 views

Saving huge volumes of data in Ethereum

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. ...
0
votes
0answers
13 views

Is it possible to create false positives, aka “throwing exception” on purpose in solidity?

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: ...
0
votes
0answers
13 views

About genesisfile

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.
1
vote
1answer
31 views

Why does Ropsten faucet show “Your account is grey listed for 0 hours and 0 minutes”?

I am requesting test ether from a Ropsten faucet, but it is showing an error. Please help me to resolve this error.
0
votes
0answers
9 views

How does specifying job parameters on Chainlink work?

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, ...
0
votes
0answers
25 views

Why does this code outputs error:“unknown account”?

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":...
1
vote
0answers
24 views

How to check current status of state variables

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/...
0
votes
0answers
18 views

When to stop importing new chain segments from Rinkeby testnet?

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 ...
0
votes
2answers
26 views

It seems impossible to perform some action and then throw returning an error?

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 ...
0
votes
0answers
13 views

Synchronization mode

What kind of node synchronization should I choose to work with a centralized exchange? Is there enough quick synchronization, or is full synchronization necessary?
2
votes
1answer
32 views

In “msg.sender.call.value(msg.value)”, where is msg.value taken from?

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 ...
0
votes
1answer
13 views

Truffle Error: ContractName has no network configuration for its current network id (1575203139857)

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 ...
0
votes
1answer
27 views

Smart Contract deployment failed

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 ...
0
votes
1answer
13 views

If you need a server to store HTML and java script code, then what is the use of the block chain?

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 ...
0
votes
1answer
10 views

Nethereum contract.getPastEvents equivalent

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 ...
0
votes
1answer
29 views

RPC error when interacting with contract using Ganache GUI, but it works fine when using Ganache CLI

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 ...
0
votes
1answer
13 views

Deploy smart contract on Ropsten, Kovan

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 ...
0
votes
1answer
16 views

Node synchronization

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?
0
votes
0answers
18 views

Did I get this right that with delegatecall the msg.sender is the last entity that calls delegatecall (example below)?

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 ...
0
votes
0answers
5 views

Server configuration selection

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?
0
votes
1answer
23 views

How does smart contracts exactly work?

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 ...
0
votes
2answers
26 views

From ENS Name to hash AND print in console

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 ...
0
votes
0answers
13 views

Cannot use delegatecalls in Remix since either the addresses aren't displayed correcly or I cannot access the memory address?

For instance delegatecall to the same address works: function callTheOtherContract() public { require(address(this).delegatecall(bytes4(keccak256("callMe()")))); } event CallMe(...
0
votes
0answers
80 views

Any platforms that do validator selection using pre-committed hash chains?

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 ...
0
votes
0answers
21 views

Is there a way for a function to perform some code to a point and then revert without conditions (more details below…)?

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 ...
0
votes
1answer
32 views

How to download contracts by address from Etherscan using web3.js

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 ...
0
votes
1answer
19 views

Unable to invoke smart contract function from Web3j contract wrapper

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'...
1
vote
1answer
19 views

Provable/Oraclalize: How to get msg.sender in __callback

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 ...
0
votes
1answer
22 views

Cannot properly deploy smart contract with web3 1.2.4 provider in Geth 1.9.8

I have setup a private Ethereum node using the following configuration for the genesis block: { "config": { "chainId": 143, "homesteadBlock": 0, "eip150Block": 0, "eip155Block": 0,...
1
vote
1answer
19 views

How to use call, delegate call?

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)...
0
votes
1answer
23 views

Storing code in contracts

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, ...
0
votes
1answer
30 views

NodeJS + Web3 + Infura Ropsten - Error: Invalid JSON RPC response: “”

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 = ...
0
votes
1answer
17 views

Could not deploy contract with valid data

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 ...
1
vote
1answer
41 views

transactions in rpc block response sometimes have chain null and sometimes correct chain

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: ...
1
vote
1answer
42 views

Is it possible to have multiple private keys for a single public address? [duplicate]

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 ...
0
votes
0answers
47 views

Bad randomness exploitation

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 ((...
0
votes
0answers
16 views

Hourly data for Ethereum?

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=...
2
votes
0answers
20 views

How to get node info by 30303 port?

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 ...
0
votes
0answers
14 views

An error occurred while running C:\Users\path marketplace1\marketplace1\truffle-config.js! Did you forget to `npm install` your project?

I am getting this error when I try to add the truffle-config file to my project in ganache. What to do?
1
vote
1answer
21 views

How to calculate average time it takes for a transaction to be added to Ethereum blockchain?

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 ...
0
votes
1answer
23 views

What does web3.eth.Contract.transactionconfirmationblocks mean?

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 ...
0
votes
0answers
20 views

Connect ethereum node

How to configure a node and connect it to a browser so that I can perform erc20 token transactions on my site between users?
0
votes
0answers
33 views

Gas estimation errored with the following message (see below). The transaction execution will likely fail

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 ...
0
votes
0answers
24 views

How to interact with smart contracts on Ganache from Express app

How can I interact with the smart contract on ganache from my express app using Web3.js Any Tutorials?
0
votes
0answers
18 views

How to recieve notification of incoming transaction in metamask mobile in real time

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, ...
0
votes
2answers
29 views

No events where emmited. Why?

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 ...
0
votes
1answer
18 views

Stop watching events

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 ...
-1
votes
0answers
23 views

Api to get total transfer count of an ERC-721 Token

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/...
0
votes
1answer
15 views

error while installing web3 in ubuntu

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/...

15 30 50 per page