How To Listen on Specific Interfaces

btcd allows you to bind to specific interfaces which enables you to setup configurations with varying levels of complexity. The listen parameter can be specified on the command line as shown below with the -- prefix or in the configuration file without the -- prefix (as can all long command line options). The configuration file takes one entry per line.

NOTE: The listen flag can be specified multiple times to listen on multiple interfaces as a couple of the examples below illustrate.

Command Line Examples:

Flags	Comment
--listen=	all interfaces on default port which is changed by --testnet and --regtest (default)
--listen=0.0.0.0	all IPv4 interfaces on default port which is changed by --testnet and --regtest
--listen=::	all IPv6 interfaces on default port which is changed by --testnet and --regtest
--listen=:8333	all interfaces on port 8333
--listen=0.0.0.0:8333	all IPv4 interfaces on port 8333
--listen=[::]:8333	all IPv6 interfaces on port 8333
--listen=127.0.0.1:8333	only IPv4 localhost on port 8333
--listen=[::1]:8333	only IPv6 localhost on port 8333
--listen=:8336	all interfaces on non-standard port 8336
--listen=0.0.0.0:8336	all IPv4 interfaces on non-standard port 8336
--listen=[::]:8336	all IPv6 interfaces on non-standard port 8336
--listen=127.0.0.1:8337 --listen=[::1]:8333	IPv4 localhost on port 8337 and IPv6 localhost on port 8333
--listen=:8333 --listen=:8337	all interfaces on ports 8333 and 8337

The following config file would configure btcd to only listen on localhost for both IPv4 and IPv6:

[Application Options]

listen=127.0.0.1:8333
listen=[::1]:8333