UDP dumper

udp.hs

import System.Environment
import Network.Socket

main :: IO()
main = do
  args <- getArgs
  startNetworkStuff args

startNetworkStuff ["publish", target, port, msg] = do
  publish target port msg
startNetworkStuff ["subscribe", port] = do
  subscribe port
startNetworkStuff nothing = do
  putStrLn "Usage" 
  putStrLn "./pmnc publish target port"
  putStrLn "./pmnc subscribe port"

publish target port msg = do
  infos <- getAddrInfo Nothing (Just target) (Just port)
  sock <- socket (getAddrFamily infos) Datagram defaultProtocol -- why do I need Datagram AND defaultProtocol?
  retval <- sendTo sock msg (getServerAddr infos)
  putStrLn $ show retval

subscribe port = do
  infos <- getAddrInfo Nothing Nothing (Just port)
  sock <- socket (getAddrFamily infos) Datagram defaultProtocol
  bindSocket sock (getServerAddr infos)
  procMessages sock
  where procMessages sock = do (msg, _, addr) <- recvFrom sock 1024
                               putStrLn msg
                               procMessages sock

getAddrFamily = addrFamily . head
getServerAddr = addrAddress . head