Network.Socket

The Network.Socket module is for when you want full control over sockets. Essentially the entire C socket API is exposed through this module; in general the operations follow the behaviour of the C functions of the same name (consult your favourite Unix networking book).

A higher level interface to networking operations is provided through the module Network.

Types

data Socket

Constructors

MkSocket CInt Family SocketType ProtocolNumber (MVar SocketStatus)

Instances

Eq Socket

Show Socket

Typeable Socket

data Family

Address families.

A constructor being present here does not mean it is supported by the operating system: see isSupportedFamily.

Constructors

AF_UNSPEC

AF_UNIX

AF_INET

AF_INET6

AF_IMPLINK

AF_PUP

AF_CHAOS

AF_NS

AF_NBS

AF_ECMA

AF_DATAKIT

AF_CCITT

AF_SNA

AF_DECnet

AF_DLI

AF_LAT

AF_HYLINK

AF_APPLETALK

AF_ROUTE

AF_NETBIOS

AF_NIT

AF_802

AF_ISO

AF_OSI

AF_NETMAN

AF_X25

AF_AX25

AF_OSINET

AF_GOSSIP

AF_IPX

Pseudo_AF_XTP

AF_CTF

AF_WAN

AF_SDL

AF_NETWARE

AF_NDD

AF_INTF

AF_COIP

AF_CNT

Pseudo_AF_RTIP

Pseudo_AF_PIP

AF_SIP

AF_ISDN

Pseudo_AF_KEY

AF_NATM

AF_ARP

Pseudo_AF_HDRCMPLT

AF_ENCAP

AF_LINK

AF_RAW

AF_RIF

AF_NETROM

AF_BRIDGE

AF_ATMPVC

AF_ROSE

AF_NETBEUI

AF_SECURITY

AF_PACKET

AF_ASH

AF_ECONET

AF_ATMSVC

AF_IRDA

AF_PPPOX

AF_WANPIPE

AF_BLUETOOTH

Instances

Eq Family

Ord Family

Read Family

Show Family

isSupportedFamily :: Family -> Bool

Does the AF_ constant corresponding to the given family exist on this system?

data SocketType

Socket Types.

The existence of a constructor does not necessarily imply that that socket type is supported on your system: see isSupportedSocketType.

Constructors

NoSocketType

0, used in getAddrInfo hints, for example

Stream

SOCK_STREAM

Datagram

SOCK_DGRAM

Raw

SOCK_RAW

RDM

SOCK_RDM

SeqPacket

SOCK_SEQPACKET

Instances

Eq SocketType

Ord SocketType

Read SocketType

Show SocketType

Typeable SocketType

isSupportedSocketType :: SocketType -> Bool

Does the SOCK_ constant corresponding to the given SocketType exist on this system?

data SockAddr

Constructors

SockAddrInet PortNumber HostAddress

SockAddrInet6 PortNumber FlowInfo HostAddress6 ScopeID

SockAddrUnix String

Instances

Eq SockAddr

Ord SockAddr

Show SockAddr

Typeable SockAddr

data SocketStatus

Constructors

NotConnected

Bound

Listening

Connected

ConvertedToHandle

Closed

Instances

Eq SocketStatus

Show SocketStatus

Typeable SocketStatus

type HostAddress = Word32

Network byte order.

type HostAddress6 = (Word32, Word32, Word32, Word32)

Host byte order.

type FlowInfo = Word32

type ScopeID = Word32

data ShutdownCmd

Constructors

ShutdownReceive

ShutdownSend

ShutdownBoth

Instances

Typeable ShutdownCmd

type ProtocolNumber = CInt

defaultProtocol :: ProtocolNumber

This is the default protocol for a given service.

newtype PortNumber

Constructors

PortNum Word16

Instances

Enum PortNumber

Eq PortNumber

Integral PortNumber

Num PortNumber

Ord PortNumber

Real PortNumber

Show PortNumber

Typeable PortNumber

Storable PortNumber

Address operations

type HostName = String

Either a host name e.g., "haskell.org" or a numeric host address string consisting of a dotted decimal IPv4 address or an IPv6 address e.g., "192.168.0.1".

type ServiceName = String

data AddrInfo

Constructors

AddrInfo

Fields

addrFlags :: [AddrInfoFlag]

addrFamily :: Family

addrSocketType :: SocketType

addrProtocol :: ProtocolNumber

addrAddress :: SockAddr

addrCanonName :: Maybe String

Instances

Eq AddrInfo

Show AddrInfo

Typeable AddrInfo

Storable AddrInfo

data AddrInfoFlag

Flags that control the querying behaviour of getAddrInfo.

Constructors

AI_ADDRCONFIG

AI_ALL

AI_CANONNAME

AI_NUMERICHOST

AI_NUMERICSERV

AI_PASSIVE

AI_V4MAPPED

Instances

Eq AddrInfoFlag

Read AddrInfoFlag

Show AddrInfoFlag

Typeable AddrInfoFlag

addrInfoFlagImplemented :: AddrInfoFlag -> Bool

Indicate whether the given AddrInfoFlag will have any effect on this system.

defaultHints :: AddrInfo

Default hints for address lookup with getAddrInfo. The values of the addrAddress and addrCanonName fields are undefined, and are never inspected by getAddrInfo.

getAddrInfo

Arguments

:: Maybe AddrInfo

preferred socket type or protocol

-> Maybe HostName

host name to look up

-> Maybe ServiceName

service name to look up

-> IO [AddrInfo]

resolved addresses, with best first

Resolve a host or service name to one or more addresses. The AddrInfo values that this function returns contain SockAddr values that you can pass directly to connect or bind.

This function is protocol independent. It can return both IPv4 and IPv6 address information.

The AddrInfo argument specifies the preferred query behaviour, socket options, or protocol. You can override these conveniently using Haskell's record update syntax on defaultHints, for example as follows:

   myHints = defaultHints { addrFlags = [AI_ADDRCONFIG, AI_CANONNAME] }

Values for addrFlags control query behaviour. The supported flags are as follows:

AI_PASSIVE

If no HostName value is provided, the network address in each SockAddr will be left as a wild card, i.e. as either iNADDR_ANY or iN6ADDR_ANY. This is useful for server applications that will accept connections from any client.

AI_CANONNAME

The addrCanonName field of the first returned AddrInfo will contain the canonical name of the host.

AI_NUMERICHOST

The HostName argument must be a numeric address in string form, and network name lookups will not be attempted.

Note: Although the following flags are required by RFC 3493, they may not have an effect on all platforms, because the underlying network stack may not support them. To see whether a flag from the list below will have any effect, call addrInfoFlagImplemented.

AI_NUMERICSERV

The ServiceName argument must be a port number in string form, and service name lookups will not be attempted.

AI_ADDRCONFIG

The list of returned AddrInfo values will only contain IPv4 addresses if the local system has at least one IPv4 interface configured, and likewise for IPv6.

AI_V4MAPPED

If an IPv6 lookup is performed, and no IPv6 addresses are found, IPv6-mapped IPv4 addresses will be returned.

AI_ALL

If AI_ALL is specified, return all matching IPv6 and IPv4 addresses. Otherwise, this flag has no effect.

You must provide a Just value for at least one of the HostName or ServiceName arguments. HostName can be either a numeric network address (dotted quad for IPv4, colon-separated hex for IPv6) or a hostname. In the latter case, its addresses will be looked up unless AI_NUMERICHOST is specified as a hint. If you do not provide a HostName value and do not set AI_PASSIVE as a hint, network addresses in the result will contain the address of the loopback interface.

If the query fails, this function throws an IO exception instead of returning an empty list. Otherwise, it returns a non-empty list of AddrInfo values.

There are several reasons why a query might result in several values. For example, the queried-for host could be multihomed, or the service might be available via several protocols.

Note: the order of arguments is slightly different to that defined for getaddrinfo in RFC 2553. The AddrInfo parameter comes first to make partial application easier.

Example: let hints = defaultHints { addrFlags = [AI_ADDRCONFIG, AI_CANONNAME] } addrs <- getAddrInfo (Just hints) (Just www.haskell.org) (Just http) let addr = head addrs sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr) connect sock (addrAddress addr)

data NameInfoFlag

Constructors

NI_DGRAM

NI_NAMEREQD

NI_NOFQDN

NI_NUMERICHOST

NI_NUMERICSERV

Instances

Eq NameInfoFlag

Read NameInfoFlag

Show NameInfoFlag

Typeable NameInfoFlag

getNameInfo

Arguments

:: [NameInfoFlag]

flags to control lookup behaviour

-> Bool

whether to look up a hostname

-> Bool

whether to look up a service name

-> SockAddr

the address to look up

-> IO (Maybe HostName, Maybe ServiceName)

Resolve an address to a host or service name. This function is protocol independent.

The list of NameInfoFlag values controls query behaviour. The supported flags are as follows:

NI_NOFQDN

If a host is local, return only the hostname part of the FQDN.

NI_NUMERICHOST

The name of the host is not looked up. Instead, a numeric representation of the host's address is returned. For an IPv4 address, this will be a dotted-quad string. For IPv6, it will be colon-separated hexadecimal.

NI_NUMERICSERV

The name of the service is not looked up. Instead, a numeric representation of the service is returned.

NI_NAMEREQD

If the hostname cannot be looked up, an IO error is thrown.

NI_DGRAM

Resolve a datagram-based service name. This is required only for the few protocols that have different port numbers for their datagram-based versions than for their stream-based versions.

Hostname and service name lookups can be expensive. You can specify which lookups to perform via the two Bool arguments. If one of these is False, the corresponding value in the returned tuple will be Nothing, and no lookup will be performed.

If a host or service's name cannot be looked up, then the numeric form of the address or service will be returned.

If the query fails, this function throws an IO exception.

Example: (hostName, _) <- getNameInfo [] True False myAddress

Socket operations

socket :: Family -> SocketType -> ProtocolNumber -> IO Socket

Create a new socket using the given address family, socket type and protocol number. The address family is usually AF_INET, AF_INET6, or AF_UNIX. The socket type is usually Stream or Datagram. The protocol number is usually defaultProtocol. If AF_INET6 is used, the IPv6Only socket option is set to 0 so that both IPv4 and IPv6 can be handled with one socket.

socketPair :: Family -> SocketType -> ProtocolNumber -> IO (Socket, Socket)

Build a pair of connected socket objects using the given address family, socket type, and protocol number. Address family, socket type, and protocol number are as for the socket function above. Availability: Unix.

connect :: Socket -> SockAddr -> IO ()

Connect to a remote socket at address.

bind :: Socket -> SockAddr -> IO ()

Bind the socket to an address. The socket must not already be bound. The Family passed to bind must be the same as that passed to socket. If the special port number aNY_PORT is passed then the system assigns the next available use port.

listen :: Socket -> Int -> IO ()

Listen for connections made to the socket. The second argument specifies the maximum number of queued connections and should be at least 1; the maximum value is system-dependent (usually 5).

accept :: Socket -> IO (Socket, SockAddr)

Accept a connection. The socket must be bound to an address and listening for connections. The return value is a pair (conn, address) where conn is a new socket object usable to send and receive data on the connection, and address is the address bound to the socket on the other end of the connection.

getPeerName :: Socket -> IO SockAddr

getSocketName :: Socket -> IO SockAddr

getPeerCred :: Socket -> IO (CUInt, CUInt, CUInt)

Returns the processID, userID and groupID of the socket's peer.

Only available on platforms that support SO_PEERCRED on domain sockets.

socketPort :: Socket -> IO PortNumber

socketToHandle :: Socket -> IOMode -> IO Handle

Turns a Socket into an Handle. By default, the new handle is unbuffered. Use hSetBuffering to change the buffering.

Note that since a Handle is automatically closed by a finalizer when it is no longer referenced, you should avoid doing any more operations on the Socket after calling socketToHandle. To close the Socket after socketToHandle, call hClose on the Handle.

Sending and receiving data

Do not use the send and recv functions defined in this module in new code, as they incorrectly represent binary data as a Unicode string. As a result, these functions are inefficient and may lead to bugs in the program. Instead use the send and recv functions defined in the ByteString module.

sendTo :: Socket -> String -> SockAddr -> IO Int

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.

NOTE: blocking on Windows unless you compile with -threaded (see GHC ticket #1129)

sendBufTo :: Socket -> Ptr a -> Int -> SockAddr -> IO Int

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.

recvFrom :: Socket -> Int -> IO (String, Int, SockAddr)

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

NOTE: blocking on Windows unless you compile with -threaded (see GHC ticket #1129)

recvBufFrom :: Socket -> Ptr a -> Int -> IO (Int, SockAddr)

Receive data from the socket, writing it into buffer instead of creating a new string. The socket need not be in a connected state. Returns (nbytes, address) where nbytes is the number of bytes received and address is a SockAddr representing the address of the sending socket.

NOTE: blocking on Windows unless you compile with -threaded (see GHC ticket #1129)

send :: Socket -> String -> IO Int

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.

recv :: Socket -> Int -> IO String

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.

recvLen :: Socket -> Int -> IO (String, Int)

inet_addr :: String -> IO HostAddress

inet_ntoa :: HostAddress -> IO String

shutdown :: Socket -> ShutdownCmd -> IO ()

Shut down one or both halves of the connection, depending on the second argument to the function. If the second argument is ShutdownReceive, further receives are disallowed. If it is ShutdownSend, further sends are disallowed. If it is ShutdownBoth, further sends and receives are disallowed.

close :: Socket -> IO ()

Close the socket. All future operations on the socket object will fail. The remote end will receive no more data (after queued data is flushed).

Predicates on sockets

isConnected :: Socket -> IO Bool

isBound :: Socket -> IO Bool

isListening :: Socket -> IO Bool

isReadable :: Socket -> IO Bool

isWritable :: Socket -> IO Bool

Socket options

data SocketOption

Socket options for use with setSocketOption and getSocketOption.

The existence of a constructor does not imply that the relevant option is supported on your system: see isSupportedSocketOption

Constructors

Debug

SO_DEBUG

ReuseAddr

SO_REUSEADDR

Type

SO_TYPE

SoError

SO_ERROR

DontRoute

SO_DONTROUTE

Broadcast

SO_BROADCAST

SendBuffer

SO_SNDBUF

RecvBuffer

SO_RCVBUF

KeepAlive

SO_KEEPALIVE

OOBInline

SO_OOBINLINE

TimeToLive

IP_TTL

MaxSegment

TCP_MAXSEG

NoDelay

TCP_NODELAY

Cork

TCP_CORK

Linger

SO_LINGER

ReusePort

SO_REUSEPORT

RecvLowWater

SO_RCVLOWAT

SendLowWater

SO_SNDLOWAT

RecvTimeOut

SO_RCVTIMEO

SendTimeOut

SO_SNDTIMEO

UseLoopBack

SO_USELOOPBACK

IPv6Only

IPV6_V6ONLY

Instances

Show SocketOption

Typeable SocketOption

isSupportedSocketOption :: SocketOption -> Bool

Does the SocketOption exist on this system?

getSocketOption :: Socket -> SocketOption -> IO Int

Get a socket option that gives an Int value. There is currently no API to get e.g. the timeval socket options

setSocketOption :: Socket -> SocketOption -> Int -> IO ()

Set a socket option that expects an Int value. There is currently no API to set e.g. the timeval socket options

File descriptor transmission

sendFd :: Socket -> CInt -> IO ()

recvFd :: Socket -> IO CInt

Special constants

aNY_PORT :: PortNumber

iNADDR_ANY :: HostAddress

The IPv4 wild card address.

iN6ADDR_ANY :: HostAddress6

The IPv6 wild card address.

sOMAXCONN :: Int

sOL_SOCKET :: Int

sCM_RIGHTS :: Int

maxListenQueue :: Int

Initialisation

withSocketsDo :: IO a -> IO a

On Windows operating systems, the networking subsystem has to be initialised using withSocketsDo before any networking operations can be used. eg.

 main = withSocketsDo $ do {...}

Although this is only strictly necessary on Windows platforms, it is harmless on other platforms, so for portability it is good practice to use it all the time.

Very low level operations

fdSocket :: Socket -> CInt

mkSocket :: CInt -> Family -> SocketType -> ProtocolNumber -> SocketStatus -> IO Socket

Deprecated aliases

These aliases are deprecated and should not be used in new code. They will be removed in some future version of the package.

bindSocket :: Socket -> SockAddr -> IO ()

Deprecated alias for bind.

sClose :: Socket -> IO ()

Deprecated alias for close.

sIsConnected :: Socket -> IO Bool

Deprecated alias for isConnected.

sIsBound :: Socket -> IO Bool

Deprecated alias for isBound.

sIsListening :: Socket -> IO Bool

Deprecated alias for isListening.

sIsReadable :: Socket -> IO Bool

Deprecated alias for isReadable.

sIsWritable :: Socket -> IO Bool

Deprecated alias for isWritable.

Internal

The following are exported ONLY for use in the BSD module and should not be used anywhere else.

packFamily :: Family -> CInt

unpackFamily :: CInt -> Family

packSocketType :: SocketType -> CInt