'ERROR: brownie.exceptions.RPCConnectionError: Able to launch RPC client, but unable to connect

The ganache-cli is unable to connect to the mainnet fork, as a result of which I can't run brownie test --networks mainnet-fork

My test.py file looks like this:

from brownie import Lottery, accounts, network, config

def test_eth_amount():
    account = accounts[0]
    lottery = Lottery.deploy(
        config["networks"][network.show_active()]["eth_usd_price_feed"],
        {"from": account},
    )
    print(lottery)
    assert lottery.getEntranceFee() > 18000000000000000
    assert lottery.getEntranceFee() < 21000000000000000

And brownie-config file is:

dependencies:
  # - <organization/repo>@<version>
  - smartcontractkit/[email protected]
compiler:
  solc:
    remappings:
      - '@chainlink=smartcontractkit/[email protected]'
      # - '@chainlink=smartcontractkit/[email protected]'
# dotenv: .env
networks:
  mainnet-fork:
    eth_usd_price_feed: '0x5f4ec3df9cbd43714fe2740f5e3616155c5b8419'

But even then brownie can't connect to mainnet-fork!

The error message looks like this:

Launching 'ganache-cli.cmd --accounts 10 --fork https://eth-mainnet.alchemyapi.io/v2/w1kKuepExg3kpo_V4Dr4XHArsk3IWb0Y --mnemonic brownie --port 8545 --hardfork istanbul'...     
Terminating local RPC client...
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\_pytest\main.py", line 269, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\_pytest\main.py", line 322, in _main
INTERNALERROR>     config.hook.pytest_collection(session=session)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_hooks.py", line 265, in __call__
INTERNALERROR>     return self._hookexec(self.name, self.get_hookimpls(), kwargs, firstresult)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_manager.py", line 80, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_callers.py", line 60, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_result.py", line 60, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_callers.py", line 39, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\_pytest\main.py", line 333, in pytest_collection
INTERNALERROR>     session.perform_collect()
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\_pytest\main.py", line 641, in perform_collect
INTERNALERROR>     hook.pytest_collection_finish(session=self)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_hooks.py", line 265, in __call__
INTERNALERROR>     return self._hookexec(self.name, self.get_hookimpls(), kwargs, firstresult)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_manager.py", line 80, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\pluggy\_callers.py", line 55, in _multicall
INTERNALERROR>     gen.send(outcome)
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\brownie\test\managers\runner.py", line 258, in pytest_collection_finish       
INTERNALERROR>     brownie.network.connect(CONFIG.argv["network"])
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\brownie\network\main.py", line 50, in connect
INTERNALERROR>     rpc.launch(active["cmd"], **active["cmd_settings"])
INTERNALERROR>   File "c:\users\hp\development\demos\brownie_simple_storage\venv\lib\site-packages\brownie\network\rpc\__init__.py", line 95, in launch
INTERNALERROR>     raise RPCConnectionError(cmd, self.process, uri)
INTERNALERROR> brownie.exceptions.RPCConnectionError: Able to launch RPC client, but unable to connect.
INTERNALERROR>
INTERNALERROR> Command: ganache-cli
INTERNALERROR> URI: https://127.0.0.1:8545
INTERNALERROR> Exit Code: 15

My mainnet-fork network details also doesn't seem suspicious:

Network 'mainnet-fork' has been modified
  └─mainnet-fork
    ├─id: mainnet-fork
    ├─cmd: ganache-cli
    ├─cmd_settings: {'accounts': 10, 'fork': 'https://eth-mainnet.alchemyapi.io/v2/w1kKuepExg3kpo_V4Dr4XHArsk3IWb0Y', 'mnemonic': 'brownie', 'port': 8545}
    └─host: https://127.0.0.1

If the RPC doesn't connect to the proper network, It'll be difficult for me to continue with the course.

Solution 1:^[1]

Open up Ganache and check which port you have at the start. Use the same port for the mainnet-fork. I used port: 7545

Solution 2:^[2]

You just need to wait for the deploy transaction to finish:

from brownie import Lottery, accounts, network, config

def test_eth_amount():
    account = accounts[0]
    lottery = Lottery.deploy(
        config["networks"][network.show_active()]["eth_usd_price_feed"],
        {"from": account},
    )
    lottery.tx.wait(1)
    print(lottery)
    assert lottery.getEntranceFee() > 18000000000000000
    assert lottery.getEntranceFee() < 21000000000000000

Solution 3:^[3]

I had the same problem and was able to resolve it by manually creating a virtual python environment and then installing brownie with pip (instead of pipx):

Install and activate a virtual python environment in your project. Instructions here.
Install brownie using pip: pip install eth-brownie
Delete the mainnet-fork network in brownie.
Re-create the mainnet-fork network in brownie.

Tests now run as expected.

Solution 4:^[4]

i think that you should instant of creating a mainnet-fork with host=https://127.0.0.1:8545 do it with host=https://127.0.0.1:7545

Solution 5:^[5]

It looks like you have created a network using https for your localhost. Therefore, when you try to connect to it, it's refused and the RPCConnectionError is thrown. You can check it by the log you sent:

INTERNALERROR> URI: https://127.0.0.1:8545

To solve it, you can try to delete your current mainnet-fork with

brownie networks delete mainnet-fork

and recreate it using http instead of https in the host param, with

brownie networks add development mainnet-fork cmd=ganache-cli host=http://127.0.0.1 fork=...

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Umut cuscus
Solution 2	Patrick Collins
Solution 3
Solution 4	MOHAMED
Solution 5	Yuri Delgado

'ERROR: brownie.exceptions.RPCConnectionError: Able to launch RPC client, but unable to connect

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Solution 5:[5]