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 specifies which one to use.
-
{ifaddr, Address}
-
Same as {ip, Address}
. If the host has many network interfaces, this option specifies which one to use.
However, if this instead is an socket:sockaddr_in()
or socket:sockaddr_in6()
this takes precedence over any value previously set with the ip
options. If the ip
option comes after the ifaddr
option, it may be used to update its corresponding field of the ifaddr
option (the addr
field).
-
{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 appropriately.
-
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 outgoing multicast datagrams to control the scope of the multicasts.
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.