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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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2answers
250 views

Difference between public private and consortium blockchain

I am new to blockchain therefore i am trying to understand difference between private public and consortium blockchain. I do understand public blockchain but i am unable to differentiate between ...
2
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2answers
31 views

About a concept about blockchain during learning [closed]

Like a example blockchain has one core block in its Ledger/chain. Every time who used (new or old user) blockchain from his node that will clone all chain/all blocks , means one core block (because ...
3
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1answer
138 views

ether faucet error whenever i am trying to get ethers for rinkeby testnet from https://faucet.rinkeby.io/

when ever i am trying to get ethers (rinkeby) from https://faucet.rinkeby.io/ it is giving me this error. Faucet offline: context deadline exceeded even without entry my url it is giving the error. ...
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2answers
126 views

Input from IOT devices direct to the smart contracts?

I went through almost all the answers on IOT but not got the answer. I want to create a DAPP which takes temp as input from IOT device and trigger function in the smart contract. I know the options ...
2
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1answer
69 views

Difference between .sign and .signTransaction

I have this two kind of codes and I would like to know what is the difference between them: First. .sign() var tx = new Tx(rawtx); tx.sign(privateKey); Second .signTransaction() web3.eth.accounts....
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1answer
92 views

Receive data in a smart contract

How can a smart contract receive data (strings or int) from an html page? I would like to receive some information that a user con insert in a web page, in order to save them in the blockchain (for ...
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0answers
40 views

Case study : Blockchain as a service [closed]

I have a web application which has DynamoDB as the database. I want to store some SCORE in a DynamoDB table. How can I restrict this SCORE to only some set of people in my web application can modify ...
2
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2answers
56 views

send() or transfer() functions always fail

I created a few code below pragma solidity ^0.4.19; contract SendAndTransferExample { function SimpleSendToAccount() public returns(bool) { return msg.sender.send(10000000000000000000); ...
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0answers
37 views

How can we get other transactions result like using window.web3.eth.getTransactionReceipt on our own transaction?

If I send a transaction, I can watch the result using window.web3.eth.getTransactionReceipt like this: tradeContract.methods.test(...args).send({ from: pubData.user.address, gas: gasAmount }) ....
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0answers
95 views

0 ETH Airdrop function with ICO contract

I see many airdrops that have been done by sending 0 ETH to the ICO contract address my question is: how to add this function to the ICO contract with the ability to start and stop at any time? and ...
2
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1answer
182 views

How to fix “Fatal: Error starting protocol stack: listen udp :30303: bind: address already in use”?

I am referring this tutorial and miner.start(1) works fine and mining is started as expected like below. INFO [09-05|15:41:26.486] Commit new mining work number=221 sealhash=1892af…...
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0answers
56 views

(UPDATED) Send signed transaction interacting with a contract [duplicate]

I have a local blockchain where I have deployed a contract. I want to interact with it sending multiple responses at the same time. For this propose, I cannot use Metamask to confirm each transaction. ...
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0answers
52 views

Monitoring Eth Transactions and Syncing Native Database transactions with Etherium Blockchain

Currently, I have a node.js application which interacts with geth through web sockets. I have a listener, web3.eth.subscribe( 'pendingTransactions', function(err, result) { if(!err) { ...
3
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1answer
42 views

How to pass token address of one contract into another contract?

I have two contracts , one is company contract to register company and get its token and other is to make transaction using that token. so how can i use that token in second smart contract ?
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3answers
65 views

what is the most suitable ERC token standard for non-tradable tokens?

If i want to make tokens for say university grading system (ex. each grade for every student in a course is a token he got ) , what's the best ERC token standard should i follow ?
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1answer
43 views

how can ethereum addresses are same between different networks (testnet & Main)?

I found, Wallet address are remain interchangeable if i switched between the different networks(Main Network , Ropsen Network & Rinkeby Network) is it assigned to particular machine IP, if not ...
3
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2answers
86 views

Process to find out an account's balance in the past

What would be the process to find out the balance of an account at a specific point in the past? Is it correct to say that we have to get the balance from the current World State Trie and then roll ...
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0answers
52 views

Interact with a contract using Web3 Wallet

I am trying to interact with a contract without a provider as Metamask/Mist. I know that web3 has an option to create a new Wallet and I have been seeing code examples about that but all of them ...
2
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1answer
58 views

Getting no space left on device while running geth --datadir ./datadir console

I am following this tutorial and while running below command. geth --datadir ./datadir console It ran for 15 hours and then returned below error. INFO [08-31|09:54:13.343] Imported new state ...
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1answer
169 views

Smart Contract storage

I was about to create my first smart contract which I came across these questions: Where exactly the contract code gets stored, I read that it kind of stores in blockchain so does that mean every ...
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1answer
121 views

Blockchain storage in IoT applications

Studying about the Ethereum blockchain I realized that it is ideal for my project. I intend to develop a blockchain to exchange electric energy between consumers on a smart grid. The mining nodes of ...
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1answer
86 views

Installing Ganache GUI on windows 8.1

How to install Ganache UI on windows 8.1 ? I downloaded from Official website but after downloading i am unable to install it on my machine. I tried to install it through power shell but facing ...
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1answer
44 views

How to charge all gas fee to a General Master Wallet

We are currently developing a blockchain platform that deals with sending of tokens from users to users, and as you know, ETH is required as a gas fee to be paid for any ERC20 token transfer from a ...
1
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1answer
102 views

Implementing Blockchain and Converting Web App to DApp

I have my web-application which is in Angular2 (Front end) and Rails (Back end-API), now I want to implement Blockchain to this Web application, so needs to make it DApp. Here while making the DApp, ...
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1answer
152 views

Are uncle blocks unnecessary overhead on blockchain?

I have been learning about ethereum but now am stuck with conflicting thoughts about block times and stale blocks. Here is what I understood, please correct me if I am wrong. Block time for bitcoin - ...
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1answer
45 views

Events loading too slow

I have a dapp running on rinkeby at the moment, you can try it now on cryptogol.io, but I am facing a problem when reading events from the Blockchain. For example, yesterday I make the events happens, ...
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0answers
504 views

Mining hangs on Generating DAG in progress

I am trying to initialize rpc using the below command and start miner using miner.start(1); geth --rpcapi eth,web3,personal --rpc --networkid=15 Mining starts successfully with below logs but it ...
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0answers
116 views

What does total number of blocks per day mean in Etherscan?

I tried to figure out what does total number of blocks per day means here and on the Internet, but i failed. For example, the number of blocks on 26 Aug is 5947 [here https://etherscan.io/chart/blocks]...
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1answer
277 views

Automatic “Confirm Transaction” Metamask

I have a webapp and when I send a transaction I need to approve this tx by clicking "Accept" in Metamask. I would like to implement an automatic non-clickable confirmation. Is it possible? How? (...
1
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1answer
44 views

In what way does Sharding allocate transactions for each shard? state? or node selection?

In what way does Sharding allocate transactions for each shard? I know that accounts are assigned to each shard based on prefix in the account's address and each shard processes the transactions ...
1
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1answer
53 views

Smart Contract execution time through Truffle

I would like to know if there is a way to obtain the smart contract execution time when you send it to the network through Truffle. Is it possible using the test tool? through an application? I know ...
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1answer
31 views

Is blockchain always “public”?

Is the following definition of blockchain by its wikipwdia page correct? Where it is mentioned: A blockchain is a decentralized, distributed and public digital ledger ... Cannot we have a ...
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2answers
60 views

Querying the Smart Contract?

If I have a network made of IoT devices (contain 1000000 device). I need to manage them using a smart contract. And that contract contains a constant function (to avoid paying gas). How can this ...
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1answer
50 views

Solidity - function “now” result

I would like yo know what kind of format is returned by the function now. I am calling this function in a contract and sending the result like an event to my .js file. The structure that I see is ...
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0answers
17 views

What is the main difference between “light client” and “client” in sense of “functionality” and “capability”? [duplicate]

What is the main difference between "light client" and "client" in sense of "functionality and capability" ? I mean, what can a client does that a light client cannot ? (ex. sending transactions? ...
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0answers
19 views

Is “EthArmbian” an OS for running Ethereum client on “micro-processors”?

Is "EthArmbian" an OS for running Ethereum light client on "micro-processors" or "micro-controllers" ? And if yes, which micro-processors ?
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3answers
51 views

What kind of micro-processor / micro-controller are able to run Blockchain light client?

Is there any kind of micro-processor / micro-controller that can run Blockchain light client? An example can be Samsung ARTIK: https://www.artik.io However, it's too big. Is there any other similar ...
4
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1answer
83 views

Can someone share your geth export file with me?

I need to setup an archival node ASAP but the download takes around 1-2 block per second. With this speed it will finish in 2 months (if it doesn't stall, but it does, I have to restart it manually ...
0
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1answer
42 views

Why wouldn't it be good to store lots of data in ethereum logs instead of smart contract?

I'm curious where to save big data. I don't want to save it in my private db and not in ipfs. I want it to be visible on blockchain. So It's visible on blockchain etherscan If I'd go to store data in ...
0
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1answer
130 views

How to increase gas limit ethereum

I am facing this error : Error: exceeds block gas limit When i run below command it returns 5000. web3.eth.getBlock("latest").gasLimit so as per someone's suggestion 21000 gasLimit is needed to ...
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1answer
42 views

I don't really understand how mining works, anyone can help?

I am currently studying Ethereum all by myself, and am struggling to understand how mining and Proof of work work. I have read many posts and books about it but still hard to understand how the ...
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2answers
228 views

Where are finally ethereum event logs stored?

Hello it's been written many times, but as I observe none of the answers might be the one. I'm interested in the following thing. If in a smart contract I made the event , where will it be stored? in ...
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1answer
161 views

What does “third party liquidity” mean in blockchain technology?

In this what paper, it's mentioned that one of the reasons to use blockchain technology for the energy trading is: Provide 3rd party liquidity. What does "third party liquidity" mean in blockchain ...
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0answers
42 views

Port requirements for a Light-Node?

For a light client (geth --light or parity --light) running the light client protocol what are the port requirements? Incoming: Does a light client expose a port where he accepts incoming ...
3
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1answer
71 views

“Centralized Relational Databases” vs. “Decentralized Blockchain ” : Which one is really more scalable? [closed]

There are many research papers on problem of scalability of blockchains: Just as an example : An Overview of Blockchain Technology: Architecture, Consensus, and Future Trends However, (usually by ...
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0answers
29 views

How to save big data on ethereum smart contracts [duplicate]

It's been some time since I started figuring this out. I'd really appreciate your ideas and opinions. I'm building an app on ethereum smart contract. But the thing is There might be so huge big data. ...
1
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1answer
81 views

Solidity cross programming language method calling

I was wondering if it is possible for solidity to call functions of other languages. More specifically, I am planning on developing a basic distributed search engine using the ethereum blockchain and ...
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1answer
25 views

Logs from Web3.js application and Smart Contract

I would like to know where are the logs printed when I use "console.log(x)" in a web3 app. I am using Geth and Truffle to deploy smart contracts. For example, from pet-shop tutorial, if I wanna see ...
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1answer
37 views

Sound but incorrect change in Merkle-tree

From the whitepaper, The first step in in verifying block validity is: Check if the previous block referenced by the block exists and is valid. With regard to a merkle tree propogating change ...
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0answers
31 views

rinkeby inconsistent state?

I've got a very strang behaviour when running a oraclize call like in the following example: class Test is Oraclize... { uint64[] timestamps; uint64[] numbers; function pushItem(uint64 number)...