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.

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 Errno::ECONNREFUSED when sending datagrams to a non-listening server. Wrap with an exception handler to prevent raising. Example:

begin
  client.send(message, @destination)
rescue ex : Errno
  if ex.errno == Errno::ECONNREFUSED
    p ex.inspect
  end
end

Defined in:

socket/udp_socket.cr

Constructors

Instance Method Summary

Instance methods inherited from class IPSocket

local_address local_address, remote_address remote_address

Instance methods inherited from class Socket

accept accept, accept? accept?, bind(host : String, port : Int)
bind(port : Int)
bind(addr)
bind(addr, &block) bind, broadcast=(val : Bool) broadcast=, broadcast? broadcast?, close_read close_read, close_write close_write, connect(host : String, port : Int, connect_timeout = nil)
connect(addr, timeout = nil) : Nil
connect(addr, timeout = nil, &block) connect, family : Family family, getsockopt(optname, optval, level = LibC::SOL_SOCKET) getsockopt, inspect(io) inspect, keepalive=(val : Bool) keepalive=, keepalive? keepalive?, linger linger, linger=(val : Int?) linger=, listen(backlog = SOMAXCONN)
listen(backlog = SOMAXCONN, &block) listen, protocol : Protocol protocol, receive(max_message_size = 512) : Tuple(String, Address)
receive(message : Bytes) : Tuple(Int32, Address) receive, recv_buffer_size recv_buffer_size, recv_buffer_size=(val : Int32) recv_buffer_size=, reuse_address=(val : Bool) reuse_address=, reuse_address? reuse_address?, reuse_port=(val : Bool) reuse_port=, reuse_port? reuse_port?, send(message, to addr : Address)
send(message) send, send_buffer_size send_buffer_size, send_buffer_size=(val : Int32) send_buffer_size=, setsockopt(optname, optval, level = LibC::SOL_SOCKET) setsockopt, type : Type type

Constructor methods inherited from class Socket

new(fd : Int32, family, type, protocol = Protocol::IP)
new(family, type, protocol = Protocol::IP, blocking = false) new

Class methods inherited from class Socket

ip?(string : String) ip?, tcp(family : Family, blocking = false) tcp, udp(family : Family, blocking = false) udp, unix(type : Type = Type::STREAM, blocking = false) unix

Instance methods inherited from class IO::FileDescriptor

blocking blocking, blocking=(value) blocking=, close_on_exec=(arg : Bool) close_on_exec=, close_on_exec? close_on_exec?, closed? : Bool closed?, cooked(&block) cooked, cooked! cooked!, fcntl(cmd, arg = 0) fcntl, fd : Int32 fd, finalize finalize, inspect(io) inspect, noecho(&block) noecho, noecho! noecho!, pos pos, pos=(value) pos=, pretty_print(pp) pretty_print, raw(&block) raw, raw! raw!, read_timeout=(read_timeout : Time::Span)
read_timeout=(read_timeout : Nil)
read_timeout=(read_timeout : Number) read_timeout=, reopen(other : IO::FileDescriptor) reopen, seek(offset, whence : Seek = Seek::Set)
seek(offset, whence : Seek = Seek::Set, &block) seek, stat stat, tell tell, tty? tty?, write_timed_out : Bool write_timed_out, write_timed_out=(write_timed_out : Bool) write_timed_out=, write_timeout=(write_timeout : Number)
write_timeout=(write_timeout : Time::Span)
write_timeout=(write_timeout : Nil) write_timeout=

Constructor methods inherited from class IO::FileDescriptor

new(fd : Int32, blocking = false, edge_triggerable = false) new

Class methods inherited from class IO::FileDescriptor

fcntl(fd, cmd, arg = 0) fcntl

Instance methods inherited from module IO::Buffered

close : Nil close, flush flush, flush_on_newline=(flush_on_newline) flush_on_newline=, flush_on_newline? flush_on_newline?, peek : Bytes? peek, read(slice : Bytes) read, rewind rewind, sync=(sync) sync=, sync? 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) write

Instance methods inherited from module IO

<<(obj) : self <<, close close, closed? closed?, each_byte
each_byte(&block) : Nil each_byte, each_char(&block) : Nil
each_char each_char, each_line(*args, **options, &block) : Nil
each_line(*args, **options) each_line, encoding : String encoding, flush flush, gets(limit : Int, chomp = false) : String?
gets(delimiter : Char, chomp = false) : String?
gets(delimiter : String, chomp = false) : String?
gets(chomp = true) : String?
gets(delimiter : Char, limit : Int, chomp = false) : String? gets, gets_to_end : String gets_to_end, peek : Bytes? peek, print(*objects : _) : Nil
print(obj) : Nil print, printf(format_string, args : Array | Tuple) : Nil
printf(format_string, *args) : Nil printf, puts(*objects : _) : Nil
puts : Nil
puts(obj) : Nil
puts(string : String) : Nil puts, read(slice : Bytes) read, read_byte : UInt8? read_byte, read_bytes(type, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) read_bytes, read_char : Char? read_char, read_fully(slice : Bytes) read_fully, read_fully?(slice : Bytes) 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 read_utf8_byte, rewind rewind, set_encoding(encoding : String, invalid : Symbol? = nil) set_encoding, skip(bytes_count : Int) : Nil skip, skip_to_end : Nil skip_to_end, tty? : Bool tty?, write(slice : Bytes) : Nil write, write_byte(byte : UInt8) write_byte, write_bytes(object, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) write_bytes, write_utf8(slice : Bytes) write_utf8

Class methods inherited from module IO

copy(src, dst, limit : Int)
copy(src, dst) copy, pipe(read_blocking = false, write_blocking = false)
pipe(read_blocking = false, write_blocking = false, &block) pipe

Instance methods inherited from class Reference

==(other : self)
==(other) ==, dup dup, hash hash, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference)
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

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, class class, dup dup, hash hash, inspect(io : IO)
inspect inspect, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&block) tap, to_json(io : IO)
to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s
to_s(io : IO) to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&block) try, unsafe_as(type : T.class) forall T unsafe_as

Constructor methods inherited from class Object

from_json(string_or_io, root : String) : self
from_json(string_or_io) : self from_json, from_yaml(string_or_io) : self from_yaml

Constructor Detail

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

[View source]

Instance Method Detail

def receive(message : Bytes) : Tuple(Int32, IPAddress) #

Receives a binary message from the previously bound address.

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.

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

message, client_addr = server.receive

[View source]