View Source erl_epmd (kernel v9.3)

Erlang interface towards epmd

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

Summary

Functions

Called by the distribution module to resolves the Host to an IP address of a remote node.

Called by the distribution module to get which port the local node should listen to when accepting new distribution requests.

Called by net_adm:names/0. Host defaults to the localhost. Returns the names and associated port numbers of the Erlang nodes that epmd registered at the specified host. Returns {error, address} if epmd is not operational.

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.

Registers the node with epmd 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 differentiate a new node instance connecting to epmd with the same name.

This function is invoked as this module is added as a child of the erl_distribution supervisor.

Functions

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address_please(Name, Host, AddressFamily)

View Source (since OTP 21.0)
-spec address_please(Name, Host, AddressFamily) -> Success | {error, term()}
                  when
                      Name :: string(),
                      Host :: string() | inet:ip_address(),
                      AddressFamily :: inet | inet6,
                      Port :: non_neg_integer(),
                      Version :: non_neg_integer(),
                      Success :: {ok, inet:ip_address()} | {ok, inet:ip_address(), Port, Version}.

Called by the distribution module to resolves the Host to an IP address of a remote node.

As an optimization this function may also return the port and version of the remote node. If port and version are returned port_please/3 will not be called.

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listen_port_please(Name, Host)

View Source (since OTP 23.0)
-spec listen_port_please(Name, Host) -> {ok, Port}
                      when
                          Name :: atom() | string(),
                          Host :: atom() | string() | inet:ip_address(),
                          Port :: non_neg_integer().

Called by the distribution module to get which port the local node should listen to when accepting new distribution requests.

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names(Host)

View Source (since OTP 21.0)
-spec names(Host) -> {ok, [{Name, Port}]} | {error, Reason}
         when
             Host :: atom() | string() | inet:ip_address(),
             Name :: string(),
             Port :: non_neg_integer(),
             Reason :: address | file:posix().

Called by net_adm:names/0. Host defaults to the localhost. Returns the names and associated port numbers of the Erlang nodes that epmd registered at the specified host. Returns {error, address} if epmd is not operational.

Example:

(arne@dunn)1> erl_epmd:names(localhost).
{ok,[{"arne",40262}]}
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port_please(Name, Host)

View Source (since OTP 21.0)
-spec port_please(Name, Host) -> {port, Port, Version} | noport | closed | {error, term()}
               when
                   Name :: atom() | string(),
                   Host :: atom() | string() | inet:ip_address(),
                   Port :: non_neg_integer(),
                   Version :: non_neg_integer().

Equivalent to port_please(Name, Host, infinity).

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port_please(Name, Host, Timeout)

View Source (since OTP 21.0)
-spec port_please(Name, Host, Timeout) -> {port, Port, Version} | noport | closed | {error, term()}
               when
                   Name :: atom() | string(),
                   Host :: atom() | string() | inet:ip_address(),
                   Timeout :: non_neg_integer() | infinity,
                   Port :: non_neg_integer(),
                   Version :: non_neg_integer().

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.

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register_node(Name, Port)

View Source (since OTP 21.0)
-spec register_node(Name, Port) -> Result
                 when
                     Name :: string(),
                     Port :: non_neg_integer(),
                     Creation :: non_neg_integer(),
                     Result :: {ok, Creation} | {error, already_registered} | term().

Equivalent to register_node(Name, Port, inet).

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register_node(Name, Port, Driver)

View Source (since OTP 21.0)
-spec register_node(Name, Port, Driver) -> Result
                 when
                     Name :: string(),
                     Port :: non_neg_integer(),
                     Driver :: inet_tcp | inet6_tcp | inet | inet6,
                     Creation :: non_neg_integer() | -1,
                     Result :: {ok, Creation} | {error, already_registered} | term().

Registers the node with epmd 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 differentiate a new node instance connecting to epmd with the same name.

After the node has successfully registered with epmd it will automatically attempt reconnect to the daemon if the connection is broken.

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start_link()

View Source (since OTP 21.0)
-spec start_link() -> {ok, pid()} | ignore | {error, term()}.

This function is invoked as this module is added as a child of the erl_distribution supervisor.