http://localhost:8545 is the RPC port of your locally running Ethereum node software.
geth, the Go implementation of the Ethereum node software, the command line parameters to create and configure this RPC service follows:
user@Kumquat:~$ geth --help | grep rpc
--rpc Enable the HTTP-RPC server
--rpcaddr "127.0.0.1" HTTP-RPC server listening interface
--rpcport "8545" HTTP-RPC server listening port
--rpcapi "db,eth,net,web3" API's offered over the HTTP-RPC interface
--rpccorsdomain Domains from which to accept cross origin requests (browser enforced)
The defaults for
--rpcapi will allow the regis.nu webpage to connect to your local
geth node. You will however need to configure the
--rpccorsdomain to allow your web browser to get access to your local Ethereum node.
To start a node on your local machine providing the regis.nu webpage with access to your node, try:
geth --rpc --rpcaddr "127.0.0.1" --rpcport "8545" \
--rpc --rpccorsdomain "http://regis.nu" console
"http://regis.nu" will work with the regis.nu webpage. If you are having trouble connecting, start testing with
"*" to check whether the webpage can connect to your node, then find the correct setting to minimise your security risk - see Cross-origin resource sharing for more information. And note that using
"*" could be risky.
The page will firstly try connecting to your RPC port locally, then try the RPC port available at IP address 188.8.131.52 .
http://regis.nu in my web browser, then clicked on the Start button, but the website could not connect to the RPC port of my locally running
geth. I had to temporarily allow
http://localhost in my NoScript addon within my browser before the regis.nu web page was allowed to connect to my local
geth node and list my accounts.