Code to test the type annotations for LuaCATS/luasocket 's UDP module

test_udp.lua

local socket = require("socket")

local client, err = socket.udp()
local server, err = socket.udp()

assert(client, err)
assert(server, err)

---@cast server UDPSocketUnconnected
server:setsockname("127.0.0.1", 12345)
---@cast client UDPSocketConnected
client:setsockname("127.0.0.2", 12345) -- would be "*" and an ephemeral port otherwise. But also works!
client:setpeername("127.0.0.1", 12345)

-- setting an option
local option_success, option_error = server:setoption("ipv6-v6only", true)
print(option_success, option_error) -- fails because we're bind it to an IPv4 it beforehand.

-- peername
local peer_ip, peer_port = client:getpeername()
print(peer_ip, peer_port)

print(pcall(function()
	local peer_ip, peer_port = server:getpeername() --errors because its connected only
	print(peer_ip, peer_port)
end))

-- timeout
server:settimeout(0)
local timeout = server:gettimeout()
print(timeout)
client:settimeout(42)
local timeout = client:gettimeout()
print(timeout)

-- receivesfrom
server:settimeout(0)
client:settimeout(0)
client:send("hello")

local pkt, ip_err, port = server:receivefrom()
print(pkt, "from", ip_err, port) --prints hello where from

local pkt, ip_err, port = server:receivefrom()
print(pkt, ip_err, port) -- prints nil and timeout

-- can't use `from` for connected clients.
server:sendto("from server to client", "127.0.0.2", 12345)
print(pcall(function()
	local pkt, ip_err, port = client:receivefrom() --error because its unconnected only
	print(pkt, ip_err, port)
end))

--receive
-- receive is a function that can be used both by a connected and an unconnected socket.
-- works exactly like receivefrom but without the source
server:sendto("from server to client", "127.0.0.2", 12345)
local pkt, err = client:receive()
print(pkt, err)

client:send("from client to server")
local pkt, err = server:receive()
print(pkt, err)

-- also has timeouts
local pkt, err = client:receive()
print(pkt, err) -- timeout
local pkt, err = server:receive()
print(pkt, err) -- timeout

server:close()
client:close()