When I try to create a custom RPC on http://localhost:3000/ on Metamask, it keeps on trying to connect to it. It has not moved past "Connecting to Unknown Private Network" on the Metamask extension. What am I doing wrong and how to solve this issue?

  • With me this happens sometimes but when I close the metamask tab and open it again it usually fixes it.
    – jasper
    Jun 14, 2018 at 12:02

2 Answers 2


Sure you did start the RPC server on port 3000? If you use Truffle or Ganache, your (with npm run start) web application runs on port 3000, but the RPC from Ganache usually runs on or .

  • How do I know which server RPC is running on? How do I specify the server?
    – coder123
    Jun 15, 2018 at 5:01

As TheCooocy highlighted in his answer, this happens when the RPC port is run on a different port than the web application port.

 geth --identity “LocalTestNode” --rpc --rpcport 8080 --rpccorsdomain “*” --datadir ~/mychain/data/ --port 0 --nodiscover --rpcapi db,eth,net,web3,personal --networkid 1999 --maxpeers 0 console

My RPC port here was 8080 and when I did that it worked.

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