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Is there any chance to retrieve data on a database(sql) to a smart contract [duplicate]

I want to write a smart contract that gets id numbers as inputs and then retrieve data that are recorded in a database.Is there any specific database for that process.
0
votes
1answer
15 views

using account create in metamask with Nethereum

i have a doubt can i use an account created in metamask using nethereum? i tried this. var abi = @""; var addressContract = ""; var myAddress = "xxxxx"; var password = "password"; var managedAccount =...
1
vote
1answer
20 views

Connecting to a blockchain started with ganache-cli with Ganache GUI

I start a blockchain with ganache-cli, then I create a workspace in Ganache GUI the same seed phrase and port, but I keep getting this error in Ganache: I get and error this port is being used by ...
0
votes
1answer
27 views

Solidity - Creating child contract

Recent code: pragma solidity ^0.5.11; pragma experimental ABIEncoderV2; contract Master { address Pi_C_Owner; address payable public NewAuctionPayable; //Hilfsvariable um ...
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0answers
23 views

web3js transfer fund not enough gas but account has more then enough gas

I am using a private network. I am trying to transfer network gas to another account, but I get this error: Returned error: Insufficient funds. The account you tried to send transaction from does not ...
0
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1answer
34 views

web3.js keeps throwing “error: insufficient funds for gas * price + value” on ropsten

I have been chacking around the site for possible solutions but i havent found any that would solve my (probably most basic) error. The account from which i'm sending has around 1 ether and i'm ...
0
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0answers
6 views

Quorum-maker-node not starting

I have created a node in quorum-maker using my ip address but that node is not starting.If i create a node using local ip(127.0.0.1), node starts.why?
0
votes
1answer
13 views

How a node getting the last block?

When I call web3.eth.blockNumber from a specific full-node, where does it getting the last block? I know that the full-block holds part of the chain which he gets from gossiping with other full-nodes....
0
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0answers
19 views

how to write a program to check the nearest store in solidity [on hold]

contract Evcharge { using Itmap for Itmap.AddressUintMap; event Transfer(address indexed _from, address indexed _to, uint256 _value); event Approval(address indexed _owner, address indexed ...
0
votes
1answer
14 views

In ethereum private blockchain, how to get list of transactions of particular address?

I build own ethereum private blockchain.Generating address and assign to users.Now how I will get the transaction info If user make payment from any third party api to our generated address then how I ...
0
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0answers
21 views

uploading files to ipfs without refreshing page [on hold]

i was trying to upload files to ipfs via nodejs. I want to upload file async without page refreshing. And receive hash on front and jquery Ajax --> nodejs--> ipfs. div class="input-group"> <...
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2answers
19 views

How can I add mint and burn function to my erc20 contract code? [on hold]

How can I add mint and burn function to my erc20 contract code? This code is working properly but I couldn't add mint and burn function that work. Is there anyone who will help me about fixing this ...
1
vote
1answer
34 views

Value of msg.sender in call to inherited external function

I found this in the official solidity docs. The values of all members of msg, including msg.sender and msg.value can change for every external function call. This includes calls to library ...
0
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0answers
22 views

Cann't send token with looping function

Sorry, I'm a newbie on ERC721 token. Please help. I have deployed ERC721 contract in the localhost testnet. I use looping function for mint token and it works. But when I use looping function for ...
0
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0answers
6 views

How to simulate 2 accounts on the same Ropsten network using MetaMask and Remix?

I was able to deploy to the contract and everything but I wanted to see another account interacting with the contract, but on Remix only one account at a time
0
votes
1answer
33 views

Arduino Vs Raspberry pi with Ethereuem Blockcain

I already built a smart contract for Ethereum Blockchain by using truffle to track the ownership of IoT devices; Now, I'm looking to connect my smart contract with the IoT environment (node) to detect ...
0
votes
1answer
13 views

Are there any virtual IoT simulators that facilitate the connection with Ethereum Blockchain?

I already built a smart contract for Ethereum Blockchain by using truffle; Now, I'm looking to connect my smart contract with the IoT environment. So are there any IoT simulators (platform, framework,...
0
votes
0answers
23 views

JSON RPC error on Angular Truffle Box

I use angular-truffle-box to create a dapp and when i tried to create a method getAge() and deploy the contract it shows me this error: Error: Returned error: {"id":12,"jsonrpc":"2.0","error":{"code":...
0
votes
1answer
40 views

Solidity smart contract function in function [on hold]

I tried to write a smart contract like the following. There are two function of a contract: the first function makes confirmation of a condition, the second function makes a new contract, if all ...
0
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0answers
11 views

RSA signature verification: Inputs to Precompile contract

I am trying to verify an RSA signature using Ethereum smart contract. I have some doubts regarding my design. I am using the precompile at address 0X05 to generate s^e mod n, where s is the ...
0
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0answers
15 views

Can we connect custom Ethereum currency through java's web3j library ? If yes then how?

Im trying to create my own new currency using solidity and ethereum platform and also i want to create an Ewallet of my currency using java so that my ewallet could communicate through api .If u ...
0
votes
1answer
9 views

How to get exchange rates for testnets?

I would like to see what a PETH on Kovan is worth in DAI. How can you look for exchange rates on testnets?
0
votes
1answer
13 views

how to put struct “s1” values in another variable

how to put struct "s1" values in another variable. pragma solidity ^0.5.1; contract MyContract{ struct student{ int RollNo; string Name; } student public s1=student({...
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0answers
13 views

What is the networkid and chain id of truffle cli?

I am using truffle console to deploy contracts and using Nodejs/web3js to interract with it. I wanted to use ethereumjs-tx for signing transaction, here is the reference link. I am not sure ,how can ...
1
vote
0answers
12 views

How a full node knows which chain to follow?

After Istanbul fork, my full node followed the longest chain which has: Longest Chain Highest TotalDifficulty It seems that the shorter chain of the core-dev closing the gap - total difficulty ...
0
votes
1answer
11 views

methods.myMethod.call not return value I wanted

I am attempt to get an address using methods.call(). And it's something error. JS var rcAddr = "0x683d1602fa7252d49cda8ac414c1641a56e73d03"; var methodName = "Access Control"; var register = new ...
0
votes
1answer
20 views

(error_10) Please enter a valid data value (Must be hex.)MyEther Wallet

im trying to deploy smart contract on Myteherwallet but geting an error while deploying byte code of smart contact which is written in solidity remix IDE I have even tried to change the object byte ...
0
votes
1answer
14 views

rpc error with payload and exception thrown in contract code

This is the problem I get when trying to run my contract! And then when I go ahead and run it, this pops up This is my js code: import React, { Component } from 'react'; import Web3 from 'web3'; ...
0
votes
1answer
12 views

Private Ethereum blockchain Transaction Issue

Sending ether from one address to another using web3js. Getting issue of "account unlock with HTTP access is forbidden"
0
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0answers
18 views

Failed to compile <modul not found>

please help me Module not found: Can't resolve 'web3' in 'C:\Users\block\src\components' i don'k know why .. my app.js import React, { Component } from 'react'; import logo from './logo.svg'; ...
1
vote
0answers
21 views

What's Ethereum's mechanism for transitioning to new consensus rules?

In Bitcoin, historically, several ways to fork the network in have been used: User Activated Soft Fork (UASF): on a certain hardcoded blockchain height the nodes simply start enforcing the new rules ...
0
votes
1answer
13 views

Modify the state using returned variable (Array.push)

In my contact I want to have one place where I find an existing object(struct) and then use it in multiple places to read and modify it - but seems like it's not possible? contract A { struct ...
0
votes
1answer
19 views

Altcoin transfers

I sent a number of ERC20 tokens to Metamask. They are not showing in the MM wallet, but I do see them in Etherscan. I now want to sent them to a different address but I don't see how to do that. When ...
1
vote
0answers
26 views

Function selector computed differently for libraries?

As documented in various places, the function selector is computed as the first four bytes of the keccak256 hash of the function header, which consists of the function name followed by the list of ...
1
vote
0answers
19 views

During fork, how tx that was sent from full node is been mined on the two blockchains?

My full node connected to 0,...,n peers and follows the longest chain after Istanbul fork - the miner's chain. General transaction flow: full-node get the tx, validates and broadcast to its peers. ...
0
votes
1answer
9 views

Call functions from another account by default in web3

In my truffle tests, I am trying to call a function from an account other than the default account, so not accounts[0] from the below result. web3.eth.defaultAccount doesn't seem to work. web3.eth....
0
votes
1answer
13 views

Can i recover ethereum sent to and invalid address? [duplicate]

i've mistakenly pasted "2.5" in address field submitted a withdrawal request. can i get my coins back since the address is an invalid or the coin will be sent? I'm afraid i may loose my coins.
0
votes
0answers
47 views

Quorum - Actual blocknumber and eth.blockNumber mismatch

I have a 3-node quorum setup that has been running from Jan 2019. The nodes were working without a problem until Sept 18 2019 when the network started to throw errors on submitting transactions with ...
2
votes
1answer
66 views

If a function calls another function in another contract, where is the called function executed?

When a contract calls a function in another contract, is the called function executed in the same EVM as the caller function, in another EVM on the same node or in another random node?
1
vote
0answers
20 views

How a contract on Ropsten (deployed after fork) emit 3/5 events on the shorter chain while same contract on longer chain emits 5/5 of the events

General info: We have a full-node, which broadcast our txs. We have a EventSource contract which contains 5 events types. The eventSource contract deployed only after Istanbul fork. Our node was ...
0
votes
1answer
23 views

Can we send tokens with data input? [duplicate]

Can we send tokens with data input? I did a bit of research on erc20 but maybe this is quite complicated. Will erc 721 do this?
1
vote
0answers
23 views

How to get DAI using Web3.js

I'm building a Web3 app and I'm trying it out on the Kovan testnet. I'm trying to get some DAI. As far as I understand it the way to get DAI is to: Exchange ETH for WETH. Use Sai Tub contract to open ...
0
votes
0answers
19 views

Where does one see the APR fee when opening a CDP with Eth to Dai conversion?

Where can one find the APR % fee when converting my Eth to Dai using the markerdao contract? And how is the fee paid in and when does it get paid?
0
votes
1answer
28 views

Does using a very high gas limit somehow get your transactions executed slower?

I'm executing transactions on mainnet with a NodeJS script: async function send(web3, transaction, destAddr, gasPrice, privateKey) { const options = { data : transaction.encodeABI(), ...
1
vote
0answers
14 views

How to forcibly switch Geth to follow other chain and not the largest?

During the previous fork on Ropstan, my node seems to follow to the wrong chain if I understood correctly. As for now, it's on 6537730, it's the longest but major players are around 6523511. What are ...
0
votes
2answers
18 views

Check if contract exists in list

I've got a contract which creates another contracts and stores them in a list. How can I check that contract with specific index already exists? import "./User.sol"; contract Main is Ownable { ...
0
votes
1answer
15 views

what is 'UnimplementedFeatureError: Not yet implemented - FixedPointType' error?

what is 'UnimplementedFeatureError: Not yet implemented - FixedPointType' error in solidity while compiling through truffle ? How to fix it ? Using solidity compiler version - 0.5.9
0
votes
1answer
36 views

how can i count how many buyers made request to my smart contract and get earnedEther

I am using a factory contract for selling and buying goods. how can retrieve how many buyers bought and calculate how much ether earned by selling goods? here is my source code. I am new on smart ...
0
votes
1answer
36 views

Must consider things for every smart contract

When creating smart contract from scratch, what kind of things you should consider? For example: 1.Certain functions should be accessible only by creator/specific addresses 2.Fallback function Is ...
0
votes
1answer
12 views

Why do I always get “Returned values are not valid, did it run Out of Gas”?

I'm new on Ethereum blockchain and I'm working on deploy and using smart contract using truffle on my private blockchain. I have followed exactly this guide https://www.trufflesuite.com/docs/...

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