Multicast support

[gev]

Add multicast.

Tested on Linux, Windows, Mac OS.

Example:

module Discovery.Scanner where

import Control.Exception
import Control.Monad
import Data.List.NonEmpty qualified as NE
import Network.Socket
import Network.Socket.ByteString

runScanner :: HostName -> HostName -> ServiceName -> IO ()
runScanner host group port = do
    host' <- resolve host
    group' <- resolve group
    let multicast = MulticastGroup (hostAddress group'.addrAddress) Nothing
    bracket (socket AF_INET Datagram defaultProtocol) close \sock -> do
        bind sock host'.addrAddress
        setSockOpt sock AddMembership multicast
        forever do
            msg <- recv sock 1024
            print msg
  where
    resolve addr = NE.head <$> getAddrInfo Nothing (Just addr) (Just port)

hostAddress :: SockAddr -> HostAddress
hostAddress (SockAddrInet _ addr) = addr
hostAddress _ = error "Unsupported socket address"

module Discovery.Annoncer where

import Control.Concurrent
import Control.Exception
import Control.Monad
import Data.List.NonEmpty qualified as NE
import Network.Socket
import Network.Socket.ByteString

runAnnoncer :: HostName -> ServiceName -> IO ()
runAnnoncer group port = do
    group' <- resolve group
    bracket (socket AF_INET Datagram defaultProtocol) close \sock -> do
        forever do
            sendAllTo sock "hello" group'.addrAddress
            threadDelay 1_000_000
  where
    resolve addr = NE.head <$> getAddrInfo Nothing (Just addr) (Just port)

import Control.Concurrent.Async
import Control.Monad
import Discovery.Annoncer
import Discovery.Scanner

main :: IO ()
main = void $ concurrently
    do runAnnoncer "239.0.0.1" "2026"
    do runScanner "0.0.0.0" "239.0.0.1" "2026"