Network.Socket.ByteString

This module provides access to the BSD socket interface. This module is generally more efficient than the String based network functions in Socket. For detailed documentation, consult your favorite POSIX socket reference. All functions communicate failures by converting the error number to IOError.

This module is made to be imported with Socket like so:

 import Network.Socket hiding (send, sendTo, recv, recvFrom)
 import Network.Socket.ByteString

Send data to a socket

send

Arguments

:: Socket

Connected socket

-> ByteString

Data to send

-> IO Int

Number of bytes sent

Send data to the socket. The socket must be connected to a remote socket. Returns the number of bytes sent. Applications are responsible for ensuring that all data has been sent.

sendAll

Arguments

:: Socket

Connected socket

-> ByteString

Data to send

-> IO ()

Send data to the socket. The socket must be connected to a remote socket. Unlike send, this function continues to send data until either all data has been sent or an error occurs. On error, an exception is raised, and there is no way to determine how much data, if any, was successfully sent.

sendTo

Arguments

:: Socket

Socket

-> ByteString

Data to send

-> SockAddr

Recipient address

-> IO Int

Number of bytes sent

Send data to the socket. The recipient can be specified explicitly, so the socket need not be in a connected state. Returns the number of bytes sent. Applications are responsible for ensuring that all data has been sent.

sendAllTo

Arguments

:: Socket

Socket

-> ByteString

Data to send

-> SockAddr

Recipient address

-> IO ()

Send data to the socket. The recipient can be specified explicitly, so the socket need not be in a connected state. Unlike sendTo, this function continues to send data until either all data has been sent or an error occurs. On error, an exception is raised, and there is no way to determine how much data, if any, was successfully sent.

Vectored I/O

Vectored I/O, also known as scatter/gather I/O, allows multiple data segments to be sent using a single system call, without first concatenating the segments. For example, given a list of ByteStrings, xs,

 sendMany sock xs

is equivalent to

 sendAll sock (concat xs)

but potentially more efficient.

Vectored I/O are often useful when implementing network protocols that, for example, group data into segments consisting of one or more fixed-length headers followed by a variable-length body.

sendMany

Arguments

:: Socket

Connected socket

-> [ByteString]

Data to send

-> IO ()

Send data to the socket. The socket must be in a connected state. The data is sent as if the parts have been concatenated. This function continues to send data until either all data has been sent or an error occurs. On error, an exception is raised, and there is no way to determine how much data, if any, was successfully sent.

sendManyTo

Arguments

:: Socket

Socket

-> [ByteString]

Data to send

-> SockAddr

Recipient address

-> IO ()

Send data to the socket. The recipient can be specified explicitly, so the socket need not be in a connected state. The data is sent as if the parts have been concatenated. This function continues to send data until either all data has been sent or an error occurs. On error, an exception is raised, and there is no way to determine how much data, if any, was successfully sent.

Receive data from a socket

recv

Arguments

:: Socket

Connected socket

-> Int

Maximum number of bytes to receive

-> IO ByteString

Data received

Receive data from the socket. The socket must be in a connected state. This function may return fewer bytes than specified. If the message is longer than the specified length, it may be discarded depending on the type of socket. This function may block until a message arrives.

Considering hardware and network realities, the maximum number of bytes to receive should be a small power of 2, e.g., 4096.

For TCP sockets, a zero length return value means the peer has closed its half side of the connection.

recvFrom

Arguments

:: Socket

Socket

-> Int

Maximum number of bytes to receive

-> IO (ByteString, SockAddr)

Data received and sender address

Receive data from the socket. The socket need not be in a connected state. Returns (bytes, address) where bytes is a ByteString representing the data received and address is a SockAddr representing the address of the sending socket.

Example

Here are two minimal example programs using the TCP/IP protocol: a server that echoes all data that it receives back (servicing only one client) and a client using it.

 -- Echo server program
 module Main where

 import Control.Monad (unless)
 import Network.Socket hiding (recv)
 import qualified Data.ByteString as S
 import Network.Socket.ByteString (recv, sendAll)

 main :: IO ()
 main = withSocketsDo $
     do addrinfos <- getAddrInfo
                     (Just (defaultHints {addrFlags = [AI_PASSIVE]}))
                     Nothing (Just "3000")
        let serveraddr = head addrinfos
        sock <- socket (addrFamily serveraddr) Stream defaultProtocol
        bindSocket sock (addrAddress serveraddr)
        listen sock 1
        (conn, _) <- accept sock
        talk conn
        sClose conn
        sClose sock

     where
       talk :: Socket -> IO ()
       talk conn =
           do msg <- recv conn 1024
              unless (S.null msg) $ sendAll conn msg >> talk conn

 -- Echo client program
 module Main where

 import Network.Socket hiding (recv)
 import Network.Socket.ByteString (recv, sendAll)
 import qualified Data.ByteString.Char8 as C

 main :: IO ()
 main = withSocketsDo $
     do addrinfos <- getAddrInfo Nothing (Just "") (Just "3000")
        let serveraddr = head addrinfos
        sock <- socket (addrFamily serveraddr) Stream defaultProtocol
        connect sock (addrAddress serveraddr)
        sendAll sock $ C.pack "Hello, world!"
        msg <- recv sock 1024
        sClose sock
        putStr "Received "
        C.putStrLn msg