class UDPSocket
Overview
A User Datagram Protocol (UDP) socket.
UDP runs on top of the Internet Protocol (IP) and was developed for applications that do not require reliability, acknowledgement, or flow control features at the transport layer. This simple protocol provides transport layer addressing in the form of UDP ports and an optional checksum capability.
UDP is a very simple protocol. Messages, so called datagrams, are sent to other hosts on an IP network without the need to set up special transmission channels or data paths beforehand. The UDP socket only needs to be opened for communication. It listens for incoming messages and sends outgoing messages on request.
This implementation supports both IPv4 and IPv6 addresses. For IPv4 addresses you must use
Socket::Family::INET
family (default) or Socket::Family::INET6
for IPv6 # addresses.
NOTE To use UDPSocket
, you must explicitly import it with require "socket"
Usage example:
require "socket"
# Create server
server = UDPSocket.new
server.bind "localhost", 1234
# Create client and connect to server
client = UDPSocket.new
client.connect "localhost", 1234
# Send a text message to server
client.send "message"
# Receive text message from client
message, client_addr = server.receive
# Close client and server
client.close
server.close
The send
methods may sporadically fail with Socket::ConnectError
when sending datagrams
to a non-listening server.
Wrap with an exception handler to prevent raising. Example:
begin
client.send(message, @destination)
rescue ex : Socket::ConnectError
p ex.inspect
end
Defined in:
socket/udp_socket.crConstructors
Instance Method Summary
-
#join_group(address : IPAddress)
A host must become a member of a multicast group before it can receive datagrams sent to the group.
-
#leave_group(address : IPAddress)
Drops membership to the specified group.
-
#multicast_hops : Int32
Returns the current value of the
hoplimit
field on uni-cast packets. -
#multicast_hops=(val : Int)
The multicast hops option controls the
hoplimit
field on uni-cast packets. -
#multicast_interface(address : IPAddress)
For hosts with multiple interfaces, each multicast transmission is sent from the primary network interface.
-
#multicast_interface(index : UInt32)
For hosts with multiple interfaces, each multicast transmission is sent from the primary network interface.
-
#multicast_loopback=(val : Bool)
Sets whether transmitted multicast packets should be copied and sent back to the originator, if the host has joined the multicast group.
-
#multicast_loopback? : Bool
Reports whether transmitted multicast packets should be copied and sent back to the originator.
-
#receive(message : Bytes) : Tuple(Int32, IPAddress)
Receives a binary message from the previously bound address.
-
#receive(max_message_size = 512) : Tuple(String, IPAddress)
Receives a text message from the previously bound address.
Instance methods inherited from class IPSocket
bind(addr)
bind,
close
close,
connect(addr, timeout = nil, &)
connect,
local_address : Socket::IPAddress
local_address,
remote_address : Socket::IPAddress
remote_address
Instance methods inherited from class Socket
accept : Socket
accept,
accept? : Socket | Nil
accept?,
bind(host : String, port : Int) : Nilbind(port : Int)
bind(addr : Socket::Address) : Nil bind, blocking blocking, blocking=(value) blocking=, broadcast=(val : Bool) broadcast=, broadcast? : Bool broadcast?, close_on_exec=(arg : Bool) close_on_exec=, close_on_exec? close_on_exec?, close_read close_read, close_write close_write, closed? : Bool closed?, connect(host : String, port : Int, connect_timeout = nil) : Nil
connect(addr, timeout = nil) : Nil
connect(addr, timeout = nil, &) connect, family : Family family, fcntl(cmd, arg = 0) fcntl, fd fd, finalize finalize, inspect(io : IO) : Nil inspect, keepalive=(val : Bool) keepalive=, keepalive? keepalive?, linger linger, linger=(val : Int | Nil) linger=, listen(backlog : Int = SOMAXCONN) : Nil
listen(backlog : Int = SOMAXCONN, &) listen, protocol : Protocol protocol, receive(message : Bytes) : Tuple(Int32, Address)
receive(max_message_size = 512) : Tuple(String, Address) receive, recv_buffer_size : Int32 recv_buffer_size, recv_buffer_size=(val : Int32) recv_buffer_size=, reuse_address=(val : Bool) reuse_address=, reuse_address? : Bool reuse_address?, reuse_port=(val : Bool) reuse_port=, reuse_port? : Bool reuse_port?, send(message, to addr : Address) : Int32
send(message) : Int32 send, send_buffer_size : Int32 send_buffer_size, send_buffer_size=(val : Int32) send_buffer_size=, tty? tty?, type : Type type
Constructor methods inherited from class Socket
new(family : Family, type : Type, protocol : Protocol = Protocol::IP, blocking = false)new(fd, family : Family, type : Type, protocol : Protocol = Protocol::IP, blocking = false) new, tcp(family : Family, blocking = false) : self tcp, unix(type : Type = Type::STREAM, blocking = false) : self unix
Class methods inherited from class Socket
fcntl(fd, cmd, arg = 0)
fcntl,
ip?(string : String)
ip?,
udp(family : Family, blocking = false)
udp
Class methods inherited from module Crystal::System::Socket
fcntl(fd, cmd, arg = 0)
fcntl
Instance methods inherited from module IO::Evented
evented_close : Nil
evented_close,
evented_read(slice : Bytes, errno_msg : String, &) : Int32
evented_read,
evented_reopen : Nil
evented_reopen,
evented_send(slice : Bytes, errno_msg : String, &) : Int32
evented_send,
evented_write(slice : Bytes, errno_msg : String, &) : Nil
evented_write,
read_timeout : Time::Span | Nil
read_timeout,
read_timeout=(read_timeout : Number) : Numberread_timeout=(timeout : Time::Span | Nil) : Time::Span | Nil read_timeout=, write_timeout : Time::Span | Nil write_timeout, write_timeout=(write_timeout : Number) : Number
write_timeout=(timeout : Time::Span | Nil) : Time::Span | Nil write_timeout=
Instance methods inherited from module IO::Buffered
buffer_size : Int32
buffer_size,
buffer_size=(value)
buffer_size=,
close : Nil
close,
flush
flush,
flush_on_newline=(flush_on_newline)
flush_on_newline=,
flush_on_newline? : Bool
flush_on_newline?,
peek : Bytes
peek,
pos : Int64
pos,
read(slice : Bytes) : Int32
read,
read_buffering=(read_buffering)
read_buffering=,
read_buffering? : Bool
read_buffering?,
rewind
rewind,
sync=(sync)
sync=,
sync? : Bool
sync?,
unbuffered_close
unbuffered_close,
unbuffered_flush
unbuffered_flush,
unbuffered_read(slice : Bytes)
unbuffered_read,
unbuffered_rewind
unbuffered_rewind,
unbuffered_write(slice : Bytes)
unbuffered_write,
write(slice : Bytes) : Nil
write
Instance methods inherited from class IO
<<(obj) : self
<<,
close
close,
closed? : Bool
closed?,
each_byte(&) : Nileach_byte each_byte, each_char(&) : Nil
each_char each_char, each_line(*args, **options, &block : String -> ) : Nil
each_line(*args, **options) each_line, encoding : String encoding, flush flush, getb_to_end : Bytes getb_to_end, gets(limit : Int, chomp = false) : String | Nil
gets(delimiter : Char, limit : Int, chomp = false) : String | Nil
gets(delimiter : Char, chomp = false) : String | Nil
gets(delimiter : String, chomp = false) : String | Nil
gets(chomp = true) : String | Nil gets, gets_to_end : String gets_to_end, peek : Bytes | Nil peek, pos pos, pos=(value) pos=, print(obj : _) : Nil
print(*objects : _) : Nil print, printf(format_string, args : Array | Tuple) : Nil
printf(format_string, *args) : Nil printf, puts(string : String) : Nil
puts(obj : _) : Nil
puts : Nil
puts(*objects : _) : Nil puts, read(slice : Bytes) read, read_at(offset, bytesize, & : IO -> ) read_at, read_byte : UInt8 | Nil read_byte, read_bytes(type, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) read_bytes, read_char : Char | Nil read_char, read_fully(slice : Bytes) : Int32 read_fully, read_fully?(slice : Bytes) : Int32 | Nil read_fully?, read_line(*args, **options) : String read_line, read_string(bytesize : Int) : String read_string, read_utf8(slice : Bytes) read_utf8, read_utf8_byte : UInt8 | Nil read_utf8_byte, rewind rewind, seek(offset, whence : Seek = Seek::Set) seek, set_encoding(encoding : String, invalid : Symbol | Nil = nil) : Nil set_encoding, skip(bytes_count : Int) : Nil skip, skip_to_end : Nil skip_to_end, tell tell, tty? : Bool tty?, write(slice : Bytes) : Nil write, write_byte(byte : UInt8) : Nil write_byte, write_bytes(object, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) : Nil write_bytes, write_string(slice : Bytes) : Nil write_string, write_utf8(slice : Bytes) : Nil write_utf8
Class methods inherited from class IO
copy(src, dst, limit : Int) : Int64copy(src, dst) : Int64 copy, pipe(read_blocking = false, write_blocking = false) : Tuple(IO::FileDescriptor, IO::FileDescriptor)
pipe(read_blocking = false, write_blocking = false, &) pipe, same_content?(stream1 : IO, stream2 : IO) : Bool same_content?
Instance methods inherited from class Reference
==(other : self)==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup, hash(hasher) hash, initialize initialize, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference) : Bool
same?(other : Nil) same?, to_s(io : IO) : Nil to_s
Constructor methods inherited from class Reference
new
new,
unsafe_construct(address : Pointer, *args, **opts) : self
unsafe_construct
Class methods inherited from class Reference
pre_initialize(address : Pointer)
pre_initialize
Instance methods inherited from class Object
! : Bool
!,
!=(other)
!=,
!~(other)
!~,
==(other)
==,
===(other : JSON::Any)===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as
Class methods inherited from class Object
from_json(string_or_io, root : String)from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml
Constructor Detail
Instance Method Detail
A host must become a member of a multicast group before it can receive
datagrams sent to the group.
Raises Socket::Error
if an incompatible address is provided.
Drops membership to the specified group. Memberships are automatically
dropped when the socket is closed or the process exits.
Raises Socket::Error
if an incompatible address is provided.
Returns the current value of the hoplimit
field on uni-cast packets.
Datagrams with a hoplimit
of 1
are not forwarded beyond the local network.
Multicast datagrams with a hoplimit
of 0
will not be transmitted on any
network, but may be delivered locally if the sending host belongs to the
destination group and multicast loopback is enabled.
The multicast hops option controls the hoplimit
field on uni-cast packets.
If -1
is specified, the kernel will use a default value.
If a value of 0
to 255
is specified, the packet will have the specified
value as hoplimit
. Other values are considered invalid and Socket::Error
will be raised.
Datagrams with a hoplimit
of 1
are not forwarded beyond the local network.
Multicast datagrams with a hoplimit
of 0
will not be transmitted on any
network, but may be delivered locally if the sending host belongs to the
destination group and multicast loopback is enabled.
For hosts with multiple interfaces, each multicast transmission is sent
from the primary network interface. This function overrides the default
IPv4 interface address for subsequent transmissions. Setting the interface
to 0.0.0.0
will select the default interface.
Raises Socket::Error
unless the socket is IPv4 and an IPv4 address is provided.
For hosts with multiple interfaces, each multicast transmission is sent
from the primary network interface. This function overrides the default
IPv6 interface for subsequent transmissions. Setting the interface to
index 0
will select the default interface.
Sets whether transmitted multicast packets should be copied and sent back to the originator, if the host has joined the multicast group.
Reports whether transmitted multicast packets should be copied and sent back to the originator.
Receives a binary message from the previously bound address.
require "socket"
server = UDPSocket.new
server.bind "localhost", 1234
message = Bytes.new(32)
bytes_read, client_addr = server.receive(message)
Receives a text message from the previously bound address.
require "socket"
server = UDPSocket.new
server.bind("localhost", 1234)
message, client_addr = server.receive