gen_udp - Interface to UDP sockets.
Please see following description for synopsis
gen_udp(3) Erlang Module Definition gen_udp(3)
NAME
gen_udp - Interface to UDP sockets.
DESCRIPTION
This module provides functions for communicating with sockets using the
UDP protocol.
Note:
Functions that create sockets can take an optional option; {inet_back-
end, Backend} that, if specified, has to be the first option. This
selects the implementation backend towards the platform's socket API.
This is a temporary option that will be ignored in a future release.
The default is Backend = inet that selects the traditional inet_drv.c
driver. The other choice is Backend = socket that selects the new
socket module and its NIF implementation.
The system default can be changed when the node is started with the
application kernel's configuration variable inet_backend.
For gen_udp with inet_backend = socket we have tried to be as "compati-
ble" as possible which has sometimes been impossible. Here is a list of
cases when the behaviour of inet-backend inet (default) and socket are
different:
* The option read_packets is currently ignored.
DATA TYPES
option() =
{active, true | false | once | -32768..32767} |
{add_membership, {inet:ip_address(), inet:ip_address()}} |
{broadcast, boolean()} |
{buffer, integer() >= 0} |
{deliver, port | term} |
{dontroute, boolean()} |
{drop_membership, {inet:ip_address(), inet:ip_address()}} |
{header, integer() >= 0} |
{high_msgq_watermark, integer() >= 1} |
{low_msgq_watermark, integer() >= 1} |
{mode, list | binary} |
list | binary |
{multicast_if, inet:ip_address()} |
{multicast_loop, boolean()} |
{multicast_ttl, integer() >= 0} |
{priority, integer() >= 0} |
{raw,
Protocol :: integer() >= 0,
OptionNum :: integer() >= 0,
ValueBin :: binary()} |
{read_packets, integer() >= 0} |
{recbuf, integer() >= 0} |
{reuseaddr, boolean()} |
{sndbuf, integer() >= 0} |
{tos, integer() >= 0} |
{tclass, integer() >= 0} |
{ttl, integer() >= 0} |
{recvtos, boolean()} |
{recvtclass, boolean()} |
{recvttl, boolean()} |
{ipv6_v6only, boolean()}
option_name() =
active | broadcast | buffer | deliver | dontroute | header |
high_msgq_watermark | low_msgq_watermark | mode |
multicast_if | multicast_loop | multicast_ttl | priority |
{raw,
Protocol :: integer() >= 0,
OptionNum :: integer() >= 0,
ValueSpec ::
(ValueSize :: integer() >= 0) | (ValueBin :: binary())} |
read_packets | recbuf | reuseaddr | sndbuf | tos | tclass |
ttl | recvtos | recvtclass | recvttl | pktoptions |
ipv6_v6only
open_option() =
{ip, inet:socket_address()} |
{fd, integer() >= 0} |
{ifaddr, inet:socket_address()} |
inet:address_family() |
{port, inet:port_number()} |
{netns, file:filename_all()} |
{bind_to_device, binary()} |
option()
socket()
As returned by open/1,2.
EXPORTS
close(Socket) -> ok
Types:
Socket = socket()
Closes a UDP socket.
controlling_process(Socket, Pid) -> ok | {error, Reason}
Types:
Socket = socket()
Pid = pid()
Reason = closed | not_owner | badarg | inet:posix()
Assigns a new controlling process Pid to Socket. The controlling
process is the process that receives messages from the socket.
If called by any other process than the current controlling
process, {error, not_owner} is returned. If the process identi-
fied by Pid is not an existing local pid, {error, badarg} is
returned. {error, badarg} may also be returned in some cases
when Socket is closed during the execution of this function.
open(Port) -> {ok, Socket} | {error, Reason}
open(Port, Opts) -> {ok, Socket} | {error, Reason}
Types:
Port = inet:port_number()
Opts = [inet:inet_backend() | open_option()]
Socket = socket()
Reason = system_limit | inet:posix()
Associates a UDP port number (Port) with the calling process.
The following options are available:
list:
Received Packet is delivered as a list.
binary:
Received Packet is delivered as a binary.
{ip, Address}:
If the host has many network interfaces, this option speci-
fies which one to use.
{ifaddr, Address}:
Same as {ip, Address}. If the host has many network inter-
faces, this option specifies which one to use.
{fd, integer() >= 0}:
If a socket has somehow been opened without using gen_udp,
use this option to pass the file descriptor for it. If Port
is not set to 0 and/or {ip, ip_address()} is combined with
this option, the fd is bound to the specified interface and
port after it is being opened. If these options are not
specified, it is assumed that the fd is already bound appro-
priately.
inet6:
Sets up the socket for IPv6.
inet:
Sets up the socket for IPv4.
local:
Sets up a Unix Domain Socket. See inet:local_address()
{udp_module, module()}:
Overrides which callback module is used. Defaults to
inet_udp for IPv4 and inet6_udp for IPv6.
{multicast_if, Address}:
Sets the local device for a multicast socket.
{multicast_loop, true | false}:
When true, sent multicast packets are looped back to the
local sockets.
{multicast_ttl, Integer}:
Option multicast_ttl changes the time-to-live (TTL) for out-
going multicast datagrams to control the scope of the multi-
casts.
Datagrams with a TTL of 1 are not forwarded beyond the local
network. Defaults to 1.
{add_membership, {MultiAddress, InterfaceAddress}}:
Joins a multicast group.
{drop_membership, {MultiAddress, InterfaceAddress}}:
Leaves a multicast group.
Opt:
See inet:setopts/2.
The returned socket Socket is used to send packets from this
port with send/4. When UDP packets arrive at the opened port, if
the socket is in an active mode, the packets are delivered as
messages to the controlling process:
{udp, Socket, IP, InPortNo, Packet} % Without ancillary data
{udp, Socket, IP, InPortNo, AncData, Packet} % With ancillary data
The message contains an AncData field if any of the socket
options recvtos, recvtclass or recvttl are active, otherwise it
does not.
If the socket is not in an active mode, data can be retrieved
through the recv/2,3 calls. Notice that arriving UDP packets
that are longer than the receive buffer option specifies can be
truncated without warning.
When a socket in {active, N} mode (see inet:setopts/2 for
details), transitions to passive ({active, false}) mode, the
controlling process is notified by a message of the following
form:
{udp_passive, Socket}
IP and InPortNo define the address from which Packet comes.
Packet is a list of bytes if option list is specified. Packet is
a binary if option binary is specified.
Default value for the receive buffer option is {recbuf, 8192}.
If Port == 0, the underlying OS assigns a free UDP port, use
inet:port/1 to retrieve it.
recv(Socket, Length) -> {ok, RecvData} | {error, Reason}
recv(Socket, Length, Timeout) -> {ok, RecvData} | {error, Reason}
Types:
Socket = socket()
Length = integer() >= 0
Timeout = timeout()
RecvData =
{Address, Port, Packet} | {Address, Port, AncData,
Packet}
Address = inet:ip_address() | inet:returned_non_ip_address()
Port = inet:port_number()
AncData = inet:ancillary_data()
Packet = string() | binary()
Reason = not_owner | timeout | inet:posix()
Receives a packet from a socket in passive mode. Optional param-
eter Timeout specifies a time-out in milliseconds. Defaults to
infinity.
If any of the socket options recvtos, recvtclass or recvttl are
active, the RecvData tuple contains an AncData field, otherwise
it does not.
send(Socket, Destination, Packet) -> ok | {error, Reason}
Types:
Socket = socket()
Destination =
{inet:ip_address(), inet:port_number()} |
inet:family_address()
Packet = iodata()
Reason = not_owner | inet:posix()
Sends a packet to the specified Destination.
This function is equivalent to send(Socket, Destination, [],
Packet).
send(Socket, Host, Port, Packet) -> ok | {error, Reason}
Types:
Socket = socket()
Host = inet:hostname() | inet:ip_address()
Port = inet:port_number() | atom()
Packet = iodata()
Reason = not_owner | inet:posix()
Sends a packet to the specified Host and Port.
This clause is equivalent to send(Socket, Host, Port, [],
Packet).
send(Socket, Destination, AncData, Packet) -> ok | {error, Reason}
Types:
Socket = socket()
Destination =
{inet:ip_address(), inet:port_number()} |
inet:family_address()
AncData = inet:ancillary_data()
Packet = iodata()
Reason = not_owner | inet:posix()
Sends a packet to the specified Destination with ancillary data
AncData.
Note:
The ancillary data AncData contains options that for this single
message override the default options for the socket, an opera-
tion that may not be supported on all platforms, and if so
return {error, einval}. Using more than one of an ancillary data
item type may also not be supported. AncData =:= [] is always
supported.
send(Socket, Destination, PortZero, Packet) ->
ok | {error, Reason}
Types:
Socket = socket()
Destination =
{inet:ip_address(), inet:port_number()} |
inet:family_address()
PortZero = inet:port_number()
Packet = iodata()
Reason = not_owner | inet:posix()
Sends a packet to the specified Destination. Since Destination
is complete, PortZero is redundant and has to be 0.
This is a legacy clause mostly for Destination = {local, Binary}
where PortZero is superfluous. It is equivalent to send(Socket,
Destination, [], Packet), the clause right above here.
send(Socket, Host, Port, AncData, Packet) -> ok | {error, Reason}
Types:
Socket = socket()
Host =
inet:hostname() | inet:ip_address() |
inet:local_address()
Port = inet:port_number() | atom()
AncData = inet:ancillary_data()
Packet = iodata()
Reason = not_owner | inet:posix()
Sends a packet to the specified Host and Port, with ancillary
data AncData.
Argument Host can be a hostname or a socket address, and Port
can be a port number or a service name atom. These are resolved
into a Destination and after that this function is equivalent to
send(Socket, Destination, AncData, Packet), read there about
ancillary data.
Ericsson AB kernel 8.2 gen_udp(3)