Error connecting to localhost after npm hardhat run

Question

I am new to deploying smart contracts with hardhat and am following a tutorial at https://dev.to/dabit3/the-complete-guide-to-full-stack-ethereum-development-3j13. However, after running npx hardhat run scripts/deploy.js --network localhost, I get the following error. Any ideas on how to fix connection issues?

HardhatError: HH108: Cannot connect to the network localhost.
    Please make sure your node is running, and check your internet connection and networks config
        at HttpProvider._fetchJsonRpcResponse (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/hardhat/src/internal/core/providers/http.ts:176:15)
        at processTicksAndRejections (node:internal/process/task_queues:93:5)
        at HttpProvider.request (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/hardhat/src/internal/core/providers/http.ts:55:29)
        at GanacheGasMultiplierProvider._isGanache (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/hardhat/src/internal/core/providers/gas-providers.ts:302:30)
        at GanacheGasMultiplierProvider.request (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/hardhat/src/internal/core/providers/gas-providers.ts:291:23)
        at EthersProviderWrapper.send (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/@nomiclabs/hardhat-ethers/src/internal/ethers-provider-wrapper.ts:13:20)
        at Object.getSigners (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/@nomiclabs/hardhat-ethers/src/internal/helpers.ts:23:20)
        at getContractFactoryByAbiAndBytecode (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/@nomiclabs/hardhat-ethers/src/internal/helpers.ts:250:21)
        at main (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/scripts/deploy.js:17:19)
    
        Caused by: FetchError: request to http://127.0.0.1:8545/ failed, reason: connect ECONNREFUSED 127.0.0.1:8545
            at ClientRequest.<anonymous> (/Users/cuneydtasoglu/Desktop/hardhat_list/blockchain/node_modules/node-fetch/lib/index.js:1461:11)
            at ClientRequest.emit (node:events:376:20)
            at Socket.socketErrorListener (node:_http_client:490:9)
            at Socket.emit (node:events:376:20)
            at emitErrorNT (node:internal/streams/destroy:188:8)
            at emitErrorCloseNT (node:internal/streams/destroy:153:3)
            at processTicksAndRejections (node:internal/process/task_queues:80:21)

Answer 1

Petr has the right solution - your local test node (which you started with npx hardhat node) needs to continue running when you deploy your smart contract.

In other words, you should:

1. Run npx hardhat node in your terminal. Leave the process running.
2. Open a new terminal window.
3. Run npx hardhat run [script-name] --network localhost

Answer 2

Similar issue when running the deploy script with the following:

npx hardhat run scripts/deploy.js --network localhost

I could fix this by using hardhat instead of localhost:

npx hardhat run scripts/deploy.js --network hardhat

Answer 3

I had the same issue with running:

npx hardhat run scripts/deploy.js --network localhost

and tried to change the solidity version, clean up the project, removed and installed the npm_modules from scratch but the only solution that I found is reviewing my /etc/hosts file. There was this record:

::1             localhost

which obviously was creating troubles for the hardhat server.

As a tip please note the WebSocket JSON-RPC server address when you run npx hardhat node to be sure at which url it's running.

Answer 4

I have had this problem. After some research, I noticed that the node version is the key. If you are using node version 17, you can downgrade it to version 16. It applies to my project.

Answer 5

I had this issue too, both in the context of connecting Hardhat to Ethereum and to Avalanche.

The following worked for me:

1. Modify /etc/hosts and delete the line ::1 localhost as mentioned by others (https://stackoverflow.com/a/69808847/6189922)
2. Run npx hardhat node. This should output a line like:

Started HTTP and WebSocket JSON-RPC server at http://127.0.0.1:8545/

3. Modify hardhat.config.ts so that the url entry under local has the same port number as the URL printed in step 2. (8545, in this case)

Your npx commands will probably work after this.

Answer 6

This problem is mainly faced only by the newbies.

1. Don't directly deploy your contract. First, you have to start your local node to deploy your contract in localhost.

2. You can start your local eth node by typing the command :: npx hardhat node

3. Now deploy the contract.