.TH erl_epmd 3erl "kernel 7.2" "Ericsson AB" "Erlang Module Definition"
.SH NAME
erl_epmd \- 
    Erlang interface towards epmd
  
.SH DESCRIPTION
.LP
This module communicates with the EPMD daemon, see epmd\&. To implement your own epmd module please see ERTS User\&'s Guide: How to Implement an Alternative Node Discovery for Erlang Distribution
.SH EXPORTS
.LP
.nf

.B
start_link() -> {ok, pid()} | ignore | {error, term()}
.br
.fi
.br
.RS
.LP
This function is invoked as this module is added as a child of the \fIerl_distribution\fR\& supervisor\&.
.RE

.LP
.nf

.B
register_node(Name, Port) -> Result
.br
.fi
.br
.nf

.B
register_node(Name, Port, Driver) -> Result
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Name = string()
.br
Port = integer() >= 0
.br
Driver = inet_tcp | inet6_tcp | inet | inet6
.br
Creation = integer() >= 0 | -1
.br
Result = {ok, Creation} | {error, already_registered} | term()
.br
.RE
.RE
.RS
.LP
Registers the node with \fIepmd\fR\& and tells epmd what port will be used for the current node\&. It returns a creation number\&. This number is incremented on each register to help with identifying if a node is reconnecting to epmd\&.
.RE

.LP
.nf

.B
port_please(Name, Host) ->
.B
               {ok, Port, Version} |
.B
               noport | closed |
.B
               {error, term()}
.br
.fi
.br
.nf

.B
port_please(Name, Host, Timeout) ->
.B
               {port, Port, Version} |
.B
               noport | closed |
.B
               {error, term()}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Name = atom() | string()
.br
Host = atom() | string() | inet:ip_address()
.br
Timeout = integer() >= 0 | infinity
.br
Port = Version = integer() >= 0
.br
.RE
.RE
.RS
.LP
Requests the distribution port for the given node of an EPMD instance\&. Together with the port it returns a distribution protocol version which has been 5 since Erlang/OTP R6\&.
.RE

.LP
.nf

.B
listen_port_please(Name, Host) -> {ok, Port}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Name = atom()
.br
Host = string() | inet:ip_address()
.br
Port = integer() >= 0
.br
.RE
.RE
.RS
.LP
Called by the distribution module to get which port the local node should listen to when accepting new distribution requests\&.
.RE

.LP
.nf

.B
address_please(Name, Host, AddressFamily) ->
.B
                  Success | {error, term()}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Name = string()
.br
Host = string() | inet:ip_address()
.br
AddressFamily = inet | inet6
.br
Port = Version = integer() >= 0
.br
Success = 
.br
    {ok, inet:ip_address()} |
.br
    {ok, inet:ip_address(), Port, Version}
.br
.RE
.RE
.RS
.LP
Called by the distribution module to resolves the \fIHost\fR\& to an IP address of a remote node\&.
.LP
As an optimization this function may also return the port and version of the remote node\&. If port and version are returned \fIport_please/3\fR\& will not be called\&.
.RE

.LP
.nf

.B
names(Host) -> {ok, [{Name, Port}]} | {error, Reason}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Host = atom() | string() | inet:ip_address()
.br
Name = string()
.br
Port = integer() >= 0
.br
Reason = address | file:posix()
.br
.RE
.RE
.RS
.LP
Called by \fInet_adm:names/0\fR\&\&. \fIHost\fR\& defaults to the localhost\&. Returns the names and associated port numbers of the Erlang nodes that \fIepmd\fR\& registered at the specified host\&. Returns \fI{error, address}\fR\& if \fIepmd\fR\& is not operational\&.
.LP
\fIExample:\fR\&
.LP
.nf

(arne@dunn)1> erl_epmd:names(localhost)\&.
{ok,[{"arne",40262}]}
.fi
.RE