IRC is used by Electrum server to find 'peers' - other Electrum servers. The current list can be seen by running:
electrum-server peers
The following config file options are used by the IRC part of Electrum server:
[server]
irc = yes
irc_nick = server_nickname
host = fqdn.host.name.tld
# report_host = fqdn.host.name.tld
# report_stratum_tcp_port = 50001
irc is used to determine whether the IRC thread will be started or
the Electrum server will run in private mode (default). In private
mode, electrum-server peers will always return an empty list.
host is a fully-qualified domain name (FQDN) of your Electrum
server. It is used both when binding the listener for incoming client
connections and as part of the realname field in IRC (see below).
report_host is a an optional fully-qualified domain name (FQDN) of
your Electrum server instead of host. It is used as part of the name
field in IRC for incoming client connections. This is useful in a NAT
setup where you bind to a private IP locally but have an external IP
set up at your router and external DNS.
report_stratum_tcp_port and report_stratum_tcp_ssl_port are
optional settings for a port number to be reported in the IRC name
field without actually binding this port locally. This is useful in a
NAT setup where you might want to bind to a high port locally but DNAT
a different possibly privileged port for inbound connections
irc_nick is a nick name that will be appended to the E_ suffix when
composing the IRC nickname to identify your server on #electrum.
Please note the IRC name field can only contain 50 chars and will be
composed of host + protocol version number + Port numbers for the
various protocols. Please check whether port numbers are cut off at
the end
Example of port forwarding using iptables: iptables -t nat -A PREROUTING -p tcp --dport 110 -j REDIRECT --to-ports 50002