Doubt: What is difference between localhost network and hardhat network?

[adityabhattad2021]

I am actually confused about difference between different local networks and chain ids.

1. What is actually the difference between chain id 31337 and 1337 which chain id is of which network?
2. What is the chain id when we run hh node in the shell?
3. When to use --network localhost and --network hardhat?
4. If anyone can please list out differences between hardhat localhost and localhost 8545.

[othaime-en]

Hardhat has two network options hardhat and node (localhost)
The hardhat network (chainId: 1337) is a run-in-process network which means that it only runs whenever you run a scripts and terminates immediately the process ends. In short it is not persistent. If you use --network hardhat hardhat automatically creates a temporary blockchain instance, runs the script, and terminates the the instance once the script runs.

On the other hand, if you wish to have a persistent blockchain network, you use --network localhost. localhost normally has a chainId of 31337. The localhost runs as a standalone daemon that you can observe and note all transactions taking place on the network. The hardhat node also allows JSON-RPC and even websocket connections to it so you could connect it to your metamask and perform local transactions on it with numerous Dapps running locally.

Use --network localhost when you want to know what is happening under the hood and get logs of all your transactions. It is also good when it comes logging error messages when a transaction fails.
Use --network hardhat when you simply want to see if your scripts are working and aren't interested in actually having a log of all transactions.
This is my understanding of the two network options.

[othaime-en]

Hey @adityabhattad2021 I'm not sure about the error you encountered with running scripts on --network hardhat. But when it comes to hardhat.config it is okay to use the same chainId on both localhost and hardhat. If you fail to specify the network in this case, it defaults to the hardhat network. It works well for me. I think it ties down to when I said the chainIds are interchangeable. You could also use 1337 on both localhost and hardhat in you config file and it will work. But when working with hardhat I'd prefer you stick to 31337 for the localhost network.

I'm glad I could help 👍

[alymurtazamemon]

@adityabhattad2021 hardhat is the default network; you do not need to do that.

[adityabhattad2021]

Hey @adityabhattad2021 I'm not sure about the error you encountered with running scripts on --network hardhat. But when it comes to hardhat.config it is okay to use the same chainId on both localhost and hardhat. If you fail to specify the network in this case, it defaults to the hardhat network. It works well for me. I think it ties down to when I said the chainIds are interchangeable. You could also use 1337 on both localhost and hardhat in you config file and it will work. But when working with hardhat I'd prefer you stick to 31337 for the localhost network.

I'm glad I could help 👍

Fair enough, thanks!

[adityabhattad2021]

@adityabhattad2021 hardhat is the default network; you do not need to do that.

Hey I don't get what you wanna say?

[othaime-en]

I think he means that you don't need to use --network hardhat because hardhat does that for you automatically.

[krakxn]

Answered objectively:

"When to use --network localhost and --network hardhat?"

• You do not have to do --network hardhat explicitly, Hardhat does so by itself. --network localhost will run w/ a chainId of 31337

"What is the chain id when we run hh node in the shell"

• hardhat node runs the test env. on our system, ie localhost. As above, it'll have a chainId of 31337

"If anyone can please list out differences between hardhat localhost and localhost 8545"

• Answered above, whereas, localhost 8545 is the server running on your system with a port of 8545. You probably see this for a HTTP connection.

"What is actually the difference between chain id 31337 and 1337 which chain id is of which network?"

• It is in almost most cases 31337 if it is on our own system; whether it be Hardhat, Localhost or whatever.
• 1337 -- I believe -- is only used for MetaMask in the course.

[adityabhattad2021]

Now I get it, thanks!

[krakxn]

All the best!