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Erlang Port Mapper Daemon

An Erlang implementation of Erlang/OTPs port mapper daemon.

The Erlang code was originally written by Peer Stritzinger (@peerst) which was a direct port of Erlang/OTPs C-implementation of EPMD.

This code is not blessed for production use just yet.

This EPMD has two levels of interfaces. The top level being an escript, epmd that emulates the behavior of Erlang/OTP's epmd. The escript utilizes the epmd application interface.

EPMD Application

Usage:

1> application:start(epmd).

=INFO REPORT==== 2-Jun-2016::17:04:38 ===
EPMD Service started
ok

Environment variables

The application respects the following erlang environment variables within the epmd scope:

address :: [string()] - If set, EPMD will listen only on the specified address(es) and the loopback address. The default behavior is to listen on all available IP addresses.
port :: non_neg_integer() - Identifies which port EPMD will listen to. Uses OS environment variable $ERL_EPMD_PORT if not set or defaults to 4369 if neither is set.
relaxed_command_check :: boolean() - Allows for the epmd to be taken down or forced node unregister by outside influence, i.e. epmd -kill and epmd -stop
delay_write :: non_neg_integer() - Simulates a busy server. Delays messages before replying.

The application respects the following optional OS environment variables:

$ERL_EPMD_ADDRESS - Expects a comma-separated list of IP addresses. Same behavior as address above.
$ERL_EPMD_PORT - Expects an integer. Same behavior as port above.
$ERL_EPMD_RELAXED_COMMAND_CHECK - Treated as true if set otherwise false. Same behavior as relaxed_command_check.

Note: $ERL_EPMD_ADDRESS and address is not yet implemented.

EPMD Escript

usage: epmd [-d|-debug] [DbgExtra...] [-address List]
            [-port No] [-daemon] [-relaxed_command_check]
       epmd [-d|-debug] [-port No] [-names|-kill|-stop name]

See the Erlang epmd manual page for info about the usage.

Regular options
    -address List
        Let epmd listen only on the comma-separated list of IP
        addresses (and on the loopback interface).
    -port No
        Let epmd listen to another port than default 4369
    -d
    -debug
        Enable debugging. This will give a log to
        the standard error stream. It will shorten
        the number of saved used node names to 5.

        If you give more than one debug flag you may
        get more debugging information.
    -daemon
        Start epmd detached (as a daemon)
    -relaxed_command_check
        Allow this instance of epmd to be killed with
        epmd -kill even if there are registered nodes.
        Also allows forced unregister (epmd -stop).

DbgExtra options
    -delay_write Seconds
        Also a simulation of a busy server. Inserts
        a delay before a reply is sent.

Interactive options
    -names
        List names registered with the currently running epmd
    -kill
        Kill the currently running epmd
        (only allowed if -names show empty database or
        -relaxed_command_check was given when epmd was started).
    -stop Name
        Forcibly unregisters a name with epmd
        (only allowed if -relaxed_command_check was given when
        epmd was started).

Note: -address, -debug and -daemon is not yet implemented.