Metamask-extension: MetaMask not connecting to local Parity node

[john-light]

Describe the bug
When I select Localhost 8545 in my network dropdown, MetaMask shows the message Connecting to Unknown Private Network... and never completes the connection to my fully-synced local Parity node. This is happening on both the old UI and the new UI, in both up-to-date Firefox and Chromium.

To Reproduce
Steps to reproduce the behavior:

1. Open MetaMask
2. Open Parity, let it fully sync
3. Select Localhost 8545 in MetaMask dropdown
4. See Connecting to Unknown Private Network... message and notice that it does not finish connecting.

Expected behavior
I expect MetaMask to connect to Parity node and allow me to continue using MetaMask while connected to Parity.

Screenshots

Browser details (please complete the following information):

• OS: Linux Mint 18.3 64-bit
• Browser: Firefox and Chromium
• MetaMask Version: 4.9.3
• Old UI or New / Beta UI? Both

Additional context
Trying to connect to Parity UI full node Parity-Ethereum v2.0.1-20180726 beta

[tmashuang]

What port is Parity open as? Are you using it via command line or as a executable?

[john-light]

@tmashuang not sure, I haven't changed any settings in the node. I am just following the instructions MetaMask published here: https://consensys.zendesk.com/hc/en-us/articles/360004060451-Using-a-Local-Node

[tmashuang]

The article described focuses on Geth, and could be outdated. From what I see, Parity uses a default port of http://localhost:8180. Try switching back to one of the default networks, select Custom RPC from the dropdown network menu, and enter http://localhost:8180 in the Custom RPC URL field.

[john-light]

Thank you for the suggestion @tmashuang. After trying with localhost:8180 MetaMask still shows the error: Connecting to Unknown Network until I change it back to mainnet or testnet.

Edit: I am using Parity via the Parity-UI. The node is fully synced with 24 peer connections.

[tmashuang]

Try using the IP instead of localhost, the one specifically in the url that Parity opens as. If the issue persists, provide background logs, and the network tab, to see what kinds of errors might be coming from the server.

[john-light]

Try using the IP instead of localhost, the one specifically in the url that Parity opens as.

I do not understand what you mean or know how to do this.

provide background logs, and the network tab, to see what kinds of errors might be coming from the server.

Where do I find the background logs and network tab?

[mannutech]

@john-light I have got it working at my end by starting the parity node as below :
parity --chain=ropsten --jsonrpc-cors="all" --jsonrpc-apis="all" --jsonrpc-interface=all
I am sure this won't be a recommended way of starting the node, but you can get started atleast

[john-light]

Thanks @mannutech I might try taking this issue up with the Parity team too and see what their recommended method is. I would prefer to do this from the UI in a way that is known to be safe. In the mean time perhaps the MetaMask documentation around this could be updated to prevent a poor experience for Parity users.

[Tbaut]

Hi guys, Thibaut from Parity.
@mannutech is opening a little bit too much the node so that it's not secure, but the idea goes in the right direction. Since Parity only allows local HTTP RPC per default, you need to specifically whitelist the domain used by Metamask using the flag jsonrpc-cors. The domain used can be figured out by opening Metamask in a new tab (top right icon in the beta version). You will find the domain in the address bar. I have it working on Firefox using parity --chain kovan --jsonrpc-cors moz-extension://ae62fc16-c916-4c24-9a36-97f5a850f25c

[john-light]

I have MetaMask connected to local Parity node following @Tbaut instructions. Thanks everyone for your help!