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Bitcoin Core listens on three ports, as can be seen by running the following command after it has started:

sudo netstat -tulpn | grep LISTEN

By default, the ports it listens on are:

  • 8332 for the RPC client (i.e. bitcoin-cli)
  • 8333 for bitcoin clients (other nodes who want to contact this node)
  • 8334 for ????

Searching for information on port 8334 does not seem to turn up anything useful.

By observation, if the port is already bound to, it does not cause a fatal error. Bitcoin Core continues to start, although the debug.log shows the following:

Unable to bind to 127.0.0.1:8334 on this computer. Bitcoin Core is probably already running.

What does Bitcoin Core use port 8334 for?

Furthermore, other ports can be overridden using command-line arguments such as -rpcport=18332 and -port=18333 or similar configuration options in bitcoin.conf. How can Bitcoin Core be made to listen on a different port number than 8334 for whatever it uses that port for?

1 Answer 1

5

It is used for incoming Tor connections.

See here and here for more info.

You can use -bind=127.0.0.1:XXXX=onion to use port XXXX instead.

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