gen_udp
Interface to UDP sockets
The gen_udp
module provides functions for communicating
with sockets using the UDP protocol.
DATA TYPES
ip_address() see inet(3) posix() see inet(3) socket() as returned by open/1,2
Functions
open(Port) -> {ok, Socket} | {error, Reason}
open(Port, Options) -> {ok, Socket} | {error, Reason}
Port = 0..65535
Options = [Opt]
Opt -- see below
Socket = socket()
Reason = 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.
{fd, int()}
-
If a socket has somehow been opened without using
gen_udp
, use this option to pass the file descriptor for it. inet6
-
Set up the socket for IPv6.
inet
-
Set up the socket for IPv4.
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, they are delivered as messages:
{udp, Socket, IP, InPortNo, Packet}
Note that arriving UDP packets that are longer than the receive buffer option specifies, might be truncated without warning.
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}
Socket = socket()
Address = string() | atom() | ip_address()
Port = 0..65535
Packet = [char()] | binary()
Reason = not_owner | 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}
Socket = socket()
Length = int()
Address = ip_address()
Port = 0..65535
Packet = [char()] | binary()
Timeout = int() | infinity
Reason = not_owner | 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
Socket = socket()
Pid = pid()
Assigns a new controlling process Pid
to
Socket
. The controlling process is the process which
receives messages from the socket.
close(Socket) -> ok | {error, Reason}
Socket = socket()
Reason = not_owner | posix()
Closes a UDP socket.