Hello everyone I started writing this application but there is some thing missing. I read this file http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf and it say that first 24 bytes are global headers , after that every packet contains pcap local header . What i am trying to do is , first trying to get the bytes of data in each packet by reading the third field incl_len in local header but my code is not behaving as it suppose . My test libcap file is http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=view&target=udp_lite_normal_coverage_8-20.pcap --http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf --http://hackage.haskell.org/packages/archive/bytestring/0.9.0.4/doc/ html/Data-ByteString-Lazy.html import Data.List import qualified Data.ByteString.Lazy as BS import qualified Data.ByteString.Lazy.Char8 as B import Control.Monad import Text.Printf import Data.Word import Data.Char import System.Time import Numeric import System.Environment hexTodec :: BS.ByteString -> Integer hexTodec lst = read $ "0x" ++ ( concatMap ( \x -> showHex x "" ) $ BS.unpack lst ) parseFile :: BS.ByteString -> Bool -> IO [ BS.ByteString ] parseFile xs revflag | BS.null xs = return [] | otherwise = do let ind =if revflag then hexTodec . BS.reverse . BS.take 4 . BS.drop 8 $ xs else hexTodec . BS.take 4 . BS.drop 8 $ xs print ind let ( x , ys ) = BS.splitAt ( fromIntegral ind ) xs --BS.putStrLn $ x tmp <- parseFile ys revflag return $ x : tmp main = do [ file ] <- getArgs contents <- BS.readFile file let ( a , rest ) = BS.splitAt 24 contents --strip global header let revflag = case BS.unpack $ BS.take 4 a of [ 0xd4 , 0xc3 , 0xb2 , 0xa1 ] -> True _ -> False p <- parseFile rest revflag print $ p !! 0 BS.putStr $ p !! 0 Regards Mukesh Tiwari