Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/network/LICENSE)
Maintainer	libraries@haskell.org
Stability	provisional
Portability	portable
Safe Haskell	None
Language	Haskell98

Network.Socket

Contents

Types
Address operations
Socket operations
- Sending and receiving data
- Predicates on sockets
Socket options
File descriptor transmission
Special constants
Initialisation
Very low level operations
Deprecated aliases
Internal

Description

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.

Synopsis

Types

data Socket Source

Represents a socket. The fields are, respectively:

File descriptor
Socket family
Socket type
Protocol number
Status flag

If you are calling the MkSocket constructor directly you should ensure you have called withSocketsDo.

Constructors

MkSocket CInt Family SocketType ProtocolNumber (MVar SocketStatus)

Instances

Eq Socket
Show Socket
Typeable * Socket

data Family Source

Address families.

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

Instances

Eq Family
Ord Family
Read Family
Show Family

isSupportedFamily :: Family -> Bool Source

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

data SocketType Source

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 Source

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

data SockAddr Source

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

Constructors

SockAddrInet PortNumber HostAddress
SockAddrInet6 PortNumber FlowInfo HostAddress6 ScopeID
SockAddrUnix String
SockAddrCan Int32

Instances

Eq SockAddr
Ord SockAddr
Show SockAddr
Typeable * SockAddr

isSupportedSockAddr :: SockAddr -> Bool Source

Is the socket address type supported on this system?

data SocketStatus Source

The status of the socket as determined by this library, not necessarily reflecting the state of the connection itself.

For example, the Closed status is applied when the close function is called.

Constructors

NotConnected	Newly created, unconnected socket
Bound	Bound, via `bind`
Listening	Listening, via `listen`
Connected	Connected or accepted, via `connect` or `accept`
ConvertedToHandle	Is now a `Handle` (via `socketToHandle`), don't touch
Closed	Closed was closed by `close`

Instances

Eq SocketStatus
Show SocketStatus
Typeable * SocketStatus

type HostAddress = Word32 Source

Network byte order.

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

Host byte order.

type FlowInfo = Word32 Source

type ScopeID = Word32 Source

data ShutdownCmd Source

Constructors

ShutdownReceive
ShutdownSend
ShutdownBoth

Instances

Typeable * ShutdownCmd

type ProtocolNumber = CInt Source

defaultProtocol :: ProtocolNumber Source

This is the default protocol for a given service.

newtype PortNumber Source

Use the Num instance (i.e. use a literal) to create a PortNumber value with the correct network-byte-ordering. You should not use the PortNum constructor. It will be removed in the next release.

Constructors

PortNum Word16

Deprecated: Do not use the PortNum constructor. Use the Num instance. PortNum will be removed in the next release.

Instances

Enum PortNumber
Eq PortNumber
Integral PortNumber
Num PortNumber
Ord PortNumber
Real PortNumber
Show PortNumber
Storable PortNumber
Typeable * PortNumber

Address operations

type HostName = String Source

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 Source

data AddrInfo Source

Constructors

AddrInfo
Fields addrFlags :: [AddrInfoFlag] addrFamily :: Family addrSocketType :: SocketType addrProtocol :: ProtocolNumber addrAddress :: SockAddr addrCanonName :: Maybe String

Instances

Eq AddrInfo
Show AddrInfo
Storable AddrInfo
Typeable * AddrInfo

data AddrInfoFlag Source

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 Source

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

defaultHints :: AddrInfo Source

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

getAddrInfo Source

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 Source

Constructors

NI_DGRAM
NI_NAMEREQD
NI_NOFQDN
NI_NUMERICHOST
NI_NUMERICSERV

Instances

Eq NameInfoFlag
Read NameInfoFlag
Show NameInfoFlag
Typeable * NameInfoFlag

getNameInfo Source

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 Source

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) Source

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 () Source

Connect to a remote socket at address.

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

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 () Source

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) Source

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 Source

getSocketName :: Socket -> IO SockAddr Source

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

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

Only available on platforms that support SO_PEERCRED or GETPEEREID(3) on domain sockets. GETPEEREID(3) returns userID and groupID. processID is always 0.

socketPort :: Socket -> IO PortNumber Source

socketToHandle :: Socket -> IOMode -> IO Handle Source

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 Source

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 Source

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) Source

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) Source

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 Source

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 Source

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) Source

sendBuf :: Socket -> Ptr Word8 -> Int -> IO Int Source

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.

recvBuf :: Socket -> Ptr Word8 -> Int -> IO Int Source

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.

inet_addr :: String -> IO HostAddress Source

inet_ntoa :: HostAddress -> IO String Source

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

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 () Source

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 Source

Determines whether close has been used on the Socket. This does not indicate any status about the socket beyond this. If the socket has been closed remotely, this function can still return True.

isBound :: Socket -> IO Bool Source

isListening :: Socket -> IO Bool Source

isReadable :: Socket -> IO Bool Source

isWritable :: Socket -> IO Bool Source

Socket options

data SocketOption Source

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
UserTimeout	TCP_USER_TIMEOUT
IPv6Only	IPV6_V6ONLY
CustomSockOpt (CInt, CInt)

Instances

Show SocketOption
Typeable * SocketOption

isSupportedSocketOption :: SocketOption -> Bool Source

Does the SocketOption exist on this system?

getSocketOption :: Socket -> SocketOption -> IO Int Source

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 () Source

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 () Source

recvFd :: Socket -> IO CInt Source

Special constants

aNY_PORT :: PortNumber Source

iNADDR_ANY :: HostAddress Source

The IPv4 wild card address.

iN6ADDR_ANY :: HostAddress6 Source

The IPv6 wild card address.

sOMAXCONN :: Int Source

sOL_SOCKET :: Int Source

sCM_RIGHTS :: Int Source

maxListenQueue :: Int Source

This is the value of SOMAXCONN, typically 128. 128 is good enough for normal network servers but is too small for high performance servers.

Initialisation

withSocketsDo :: IO a -> IO a Source

With older versions of the network library on Windows operating systems, the networking subsystem must be initialised using withSocketsDo before any networking operations can be used. eg.

main = withSocketsDo $ do {...}

It is fine to nest calls to withSocketsDo, and to perform networking operations after withSocketsDo has returned.

In newer versions of the network library it is only necessary to call withSocketsDo if you are calling the MkSocket constructor directly. However, for compatibility with older versions on Windows, it is good practice to always call withSocketsDo (it's very cheap).

Very low level operations

fdSocket :: Socket -> CInt Source

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

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 () Source

Deprecated alias for bind.

sClose :: Socket -> IO () Source

Deprecated alias for close.

sIsConnected :: Socket -> IO Bool Source

Deprecated alias for isConnected.

sIsBound :: Socket -> IO Bool Source

Deprecated alias for isBound.

sIsListening :: Socket -> IO Bool Source

Deprecated alias for isListening.

sIsReadable :: Socket -> IO Bool Source

Deprecated alias for isReadable.

sIsWritable :: Socket -> IO Bool Source

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 Source

unpackFamily :: CInt -> Family Source

packSocketType :: SocketType -> CInt Source

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
AF_CAN