class UDPSocket

• UDPSocket
• IPSocket
• Socket
• IO
• Reference
• Object

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 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:

Constructors

• .new(family : Family = Family::INET)

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.

Constructor Detail

Instance Method Detail

require "socket"

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

message = Bytes.new(32)
bytes_read, client_addr = server.receive(message)

require "socket"

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

message, client_addr = server.receive