udp

The udp package sends and receives UDP datagrams. udp::send(host, port, text) fires off a single message; udp::socket() creates a socket for anything more.

server = udp::socket().bind(19999, "127.0.0.1")

listener = task::spawn(do (s)
  msg = s.recv()
  s.send(msg["from_host"], msg["from_port"], "echo: " + msg["data"])
end, [server])

client = udp::socket().timeout(2000)
client.send("127.0.0.1", 19999, "ping")
println client.recv()["data"]   # echo: ping

task::await(listener)
client.close()
server.close()

Method	Does
bind(port, host)	Listens on a port; host defaults to all interfaces. Returns the socket.
timeout(ms)	Makes recv give up after ms milliseconds. Returns the socket.
send(host, port, data)	Sends a string or bytes.
recv(buffer_size)	Waits for a datagram and returns {data, from_host, from_port}, with data as a string.
recv_bytes(buffer_size)	Like recv, with data as bytes.
close()	Closes the socket.

recv blocks, so a server usually runs its receive loop on a task or in a while true loop of its own:

server = udp::socket().bind(5140)
while true do
  entry = server.recv()
  println "[${entry["from_host"]}] ${entry["data"]}"
end

UDP doesn’t guarantee delivery or ordering. udp is unavailable in safe mode. For TCP, see socket.

Functions

udp::socket

udp::socket()

Creates a new UDP socket.

Returns Socket

udp::send

udp::send(host, port, data)

Sends a single datagram and closes the socket immediately.

Parameter	Type	Default	Description
host	string		Destination host.
port	integer		Destination port.
data	string|bytes		Data to send.

Socket struct

A UDP socket supporting send and receive operations.

Socket.new

Socket.new()

.bind

bind(port, host = "0.0.0.0")

Binds the socket to a local port.

Parameter	Type	Default	Description
port	integer		Port number to bind.
host	string	"0.0.0.0"	Host address (default "0.0.0.0").

Returns Socket — self

.send

send(host, port, data)

Sends data to a remote host.

Parameter	Type	Default	Description
host	string		Destination host.
port	integer		Destination port.
data	string|bytes		Data to send.

Returns integer — Number of bytes sent.

.recv

recv(buffer_size = 65535)

Receives a datagram. Returns a hashmap with "data" (string), "from_host", "from_port".

Parameter	Type	Default	Description
buffer_size	integer	65535	Max bytes to receive (default 65535).

Returns hashmap — { "data": string, "from_host": string, "from_port": integer }

.recv_bytes

recv_bytes(buffer_size = 65535)

Receives a datagram. Returns raw bytes in "data" field.

Parameter	Type	Default	Description
buffer_size	integer	65535	Max bytes to receive (default 65535).

Returns hashmap — { "data": bytes, "from_host": string, "from_port": integer }

.timeout

timeout(ms)

Sets the receive timeout.

Parameter	Type	Default	Description
ms	integer		Timeout in milliseconds.

Returns Socket — self

.close

close()

Closes the socket.