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NAME
gen_udp - Interface to UDP sockets
DESCRIPTION
The gen_udp module provides functions for communicating with sockets using the UDP
protocol.
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} |
{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 |
ipv6_v6only
socket()
As returned by open/1,2.
EXPORTS
open(Port) -> {ok, Socket} | {error, Reason}
open(Port, Opts) -> {ok, Socket} | {error, Reason}
Types:
Port = inet:port_number()
Opts = [Option]
Option =
{ip, inet:ip_address()} |
{fd, integer() >= 0} |
{ifaddr, inet:ip_address()} |
inet:address_family() |
{port, inet:port_number()} |
option()
Socket = socket()
Reason = inet:posix()
Associates a UDP port number (Port) with the calling process.
The available options are:
list:
Received Packet is delivered as a list.
binary:
Received Packet is delivered as a binary.
{ip, ip_address()}:
If the host has several network interfaces, this option specifies which one to
use.
{ifaddr, ip_address()}:
Same as {ip, ip_address()}. If the host has several network interfaces, 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 will be bound to the given
interface and port after being opened. If these options are not given it is
assumed that the fd is already bound appropriately.
inet6:
Set up the socket for IPv6.
inet:
Set up the socket for IPv4.
{udp_module, module()}:
Override which callback module is used. Defaults to inet_udp for IPv4 and
inet6_udp for IPv6.
{multicast_if, Address}:
Set the local device for a multicast socket.
{multicast_loop, true | false}:
When true sent multicast packets will be looped back to the local sockets.
{multicast_ttl, Integer}:
The multicast_ttl option changes the time-to-live (TTL) for outgoing multicast
datagrams in order to control the scope of the multicasts.
Datagrams with a TTL of 1 are not forwarded beyond the local network.
Default: 1
{add_membership, {MultiAddress, InterfaceAddress}}:
Join a multicast group.
{drop_membership, {MultiAddress, InterfaceAddress}}:
Leave 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}
If the socket is not in an active mode, data can be retrieved via the recv/2,3
calls. Note that arriving UDP packets that are longer than the receive buffer
option specifies, might 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 came. Packet is a list of
bytes if the option list was specified. Packet is a binary if the option binary was
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.
send(Socket, Address, Port, Packet) -> ok | {error, Reason}
Types:
Socket = socket()
Address = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Packet = iodata()
Reason = not_owner | inet:posix()
Sends a packet to the specified address and port. The Address argument can be
either a hostname, or an IP address.
recv(Socket, Length) ->
{ok, {Address, Port, Packet}} | {error, Reason}
recv(Socket, Length, Timeout) ->
{ok, {Address, Port, Packet}} | {error, Reason}
Types:
Socket = socket()
Length = integer() >= 0
Timeout = timeout()
Address = inet:ip_address()
Port = inet:port_number()
Packet = string() | binary()
Reason = not_owner | inet:posix()
This function receives a packet from a socket in passive mode.
The optional Timeout parameter specifies a timeout in milliseconds. The default
value is infinity.
controlling_process(Socket, Pid) -> ok | {error, Reason}
Types:
Socket = socket()
Pid = pid()
Reason = closed | not_owner | inet:posix()
Assigns a new controlling process Pid to Socket. The controlling process is the
process which receives messages from the socket. If called by any other process
than the current controlling process, {error, not_owner} is returned.
close(Socket) -> ok
Types:
Socket = socket()
Closes a UDP socket.