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udp

The udp package provides UDP (User Datagram Protocol) socket communication for sending and receiving datagrams.

Package Functions

socket()

Creates a new Socket instance.

Returns Socket

send(host, port, data)

Sends a single datagram and immediately closes the socket. Convenience function for fire-and-forget sends.

Parameters

Type Name Description
string host Destination hostname
integer port Destination port
string\|bytes data Data to send

Socket

A UDP socket returned by udp::socket().

Socket.new()

Direct constructor (prefer udp::socket() factory function).

.bind(port, host?)

Binds the socket to a local port for receiving datagrams.

Parameters

Type Name Description Default
integer port Port number to bind —
string host Local address to bind "0.0.0.0"

Returns Socket (self)

.send(host, port, data)

Sends a datagram to a remote host.

Parameters

Type Name Description
string host Destination hostname
integer port Destination port
string\|bytes data Data to send

Returns

Type Description
integer Number of bytes sent

.recv(buffer_size?)

Receives a datagram. Returns the payload as a string.

Parameters

Type Name Description Default
integer buffer_size Maximum bytes to receive 65535

Returns

Type Description
hashmap { "data": string, "from_host": string, "from_port": integer }

.recv_bytes(buffer_size?)

Receives a datagram. Returns the payload as raw bytes.

Parameters

Type Name Description Default
integer buffer_size Maximum bytes to receive 65535

Returns

Type Description
hashmap { "data": bytes, "from_host": string, "from_port": integer }

.timeout(ms)

Sets a receive timeout. After the timeout, .recv() returns an empty result rather than blocking indefinitely.

Parameters

Type Name Description
integer ms Timeout in milliseconds

Returns Socket (self)

.close()

Closes the socket and releases its resources.

Examples

Simple send

import "udp"

# Fire and forget — no socket management needed
udp::send("127.0.0.1", 9999, "hello")

Echo server

import "udp"

server = udp::socket().bind(9999)
println "UDP server listening on :9999"

while true do
  msg = server.recv()
  println "From ${msg["from_host"]}:${msg["from_port"]}: ${msg["data"]}"
  server.send(msg["from_host"], msg["from_port"], "echo: " + msg["data"])
end

Echo client

import "udp"

sock = udp::socket().timeout(3000)
sock.send("127.0.0.1", 9999, "ping")

reply = sock.recv()
println reply["data"]   # echo: ping

sock.close()

Receiving raw bytes

import "udp"

sock = udp::socket().bind(5005)
pkt = sock.recv_bytes()

println "Received ${pkt["data"].size()} bytes from ${pkt["from_host"]}"
sock.close()

Log drain (syslog-style receiver)

import "udp"
import "fio"

drain = udp::socket().bind(514)
log_file = "/var/log/kiwi-drain.log"

while true do
  entry = drain.recv()
  line = "[${entry["from_host"]}] ${entry["data"]}"
  println line
  fio::append(log_file, line + "\n")
end