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.cr

Constructors

Instance Method Summary

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) : Nil
bind(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) : Number
read_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(&) : Nil
each_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) : Int64
copy(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

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

def self.new(family : Family = Family::INET) #

[View source]

Instance Method Detail

def join_group(address : IPAddress) #

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.


[View source]
def leave_group(address : IPAddress) #

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.


[View source]
def multicast_hops : Int32 #

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.


[View source]
def multicast_hops=(val : Int) #

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.


[View source]
def multicast_interface(address : IPAddress) #

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.


[View source]
def multicast_interface(index : UInt32) #

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.


[View source]
def 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.


[View source]
def multicast_loopback? : Bool #

Reports whether transmitted multicast packets should be copied and sent back to the originator.


[View source]
def receive(message : Bytes) : Tuple(Int32, IPAddress) #

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)

[View source]
def receive(max_message_size = 512) : Tuple(String, IPAddress) #

Receives a text message from the previously bound address.

require "socket"

server = UDPSocket.new
server.bind("localhost", 1234)

message, client_addr = server.receive

[View source]