The Standard ML Basis Library

The `Socket` structure

Synopsis

signature SOCKET (* OPTIONAL *) structure Socket :> SOCKET (* OPTIONAL *)

This structure provides the standard socket types, socket management, and I/O operations. The creation of sockets is relegated to domain-specific structures (such as INetSock and UnixSock).

Interface

type ('af,'sock_type) sock type 'af sock_addr type dgram type 'mode stream type passive type active structure AF : sig type addr_family = NetHostDB.addr_family val list : unit -> (string * addr_family) list val toString : addr_family -> string val fromString : string -> addr_family option end structure SOCK : sig eqtype sock_type val stream : sock_type val dgram : sock_type val list : unit -> (string * sock_type) list val toString : sock_type -> string val fromString : string -> sock_type option end structure Ctl : sig val getDEBUG : ('af, 'sock_type) sock -> bool val setDEBUG : ('af, 'sock_type) sock * bool -> unit val getREUSEADDR : ('af, 'sock_type) sock -> bool val setREUSEADDR : ('af, 'sock_type) sock * bool -> unit val getKEEPALIVE : ('af, 'sock_type) sock -> bool val setKEEPALIVE : ('af, 'sock_type) sock * bool -> unit val getDONTROUTE : ('af, 'sock_type) sock -> bool val setDONTROUTE : ('af, 'sock_type) sock * bool -> unit val getLINGER : ('af, 'sock_type) sock -> Time.time option val setLINGER : ('af, 'sock_type) sock * Time.time option -> unit val getBROADCAST : ('af, 'sock_type) sock -> bool val setBROADCAST : ('af, 'sock_type) sock * bool -> unit val getOOBINLINE : ('af, 'sock_type) sock -> bool val setOOBINLINE : ('af, 'sock_type) sock * bool -> unit val getSNDBUF : ('af, 'sock_type) sock -> int val setSNDBUF : ('af, 'sock_type) sock * int -> unit val getRCVBUF : ('af, 'sock_type) sock -> int val setRCVBUF : ('af, 'sock_type) sock * int -> unit val getTYPE : ('af, 'sock_type) sock -> SOCK.sock_type val getERROR : ('af, 'sock_type) sock -> bool val getPeerName : ('af, 'sock_type) sock -> 'af sock_addr val getSockName : ('af, 'sock_type) sock -> 'af sock_addr val getNREAD : ('af, 'sock_type) sock -> int val getATMARK : ('af, active stream) sock -> bool end val sameAddr : 'af sock_addr * 'af sock_addr -> bool val familyOfAddr : 'af sock_addr -> AF.addr_family val bind : ('af, 'sock_type) sock * 'af sock_addr -> unit val listen : ('af, passive stream) sock * int -> unit val accept : ('af, passive stream) sock -> ('af, active stream) sock * 'af sock_addr val acceptNB : ('af, passive stream) sock -> (('af, active stream) sock * 'af sock_addr) option val connect : ('af, 'sock_type) sock * 'af sock_addr -> unit val connectNB : ('af, 'sock_type) sock * 'af sock_addr -> bool val close : ('af, 'sock_type) sock -> unit datatype shutdown_mode = NO_RECVS | NO_SENDS | NO_RECVS_OR_SENDS val shutdown : ('af, 'mode stream) sock * shutdown_mode -> unit type sock_desc val sockDesc : ('af, 'sock_type) sock -> sock_desc val sameDesc : sock_desc * sock_desc -> bool val select : { rds : sock_desc list, wrs : sock_desc list, exs : sock_desc list, timeout : Time.time option } -> { rds : sock_desc list, wrs : sock_desc list, exs : sock_desc list } val ioDesc : ('af, 'sock_type) sock -> OS.IO.iodesc type out_flags = {don't_route : bool, oob : bool} type in_flags = {peek : bool, oob : bool} val sendVec : ('af, active stream) sock * Word8VectorSlice.slice -> int val sendArr : ('af, active stream) sock * Word8ArraySlice.slice -> int val sendVec' : ('af, active stream) sock * Word8VectorSlice.slice * out_flags -> int val sendArr' : ('af, active stream) sock * Word8ArraySlice.slice * out_flags -> int val sendVecNB : ('af, active stream) sock * Word8VectorSlice.slice -> int option val sendVecNB' : ('af, active stream) sock * Word8VectorSlice.slice * out_flags -> int option val sendArrNB : ('af, active stream) sock * Word8ArraySlice.slice -> int option val sendArrNB' : ('af, active stream) sock * Word8ArraySlice.slice * out_flags -> int option val recvVec : ('af, active stream) sock * int -> Word8Vector.vector val recvVec' : ('af, active stream) sock * int * in_flags -> Word8Vector.vector val recvArr : ('af, active stream) sock * Word8ArraySlice.slice -> int val recvArr' : ('af, active stream) sock * Word8ArraySlice.slice * in_flags -> int val recvVecNB : ('af, active stream) sock * int -> Word8Vector.vector option val recvVecNB' : ('af, active stream) sock * int * in_flags -> Word8Vector.vector option val recvArrNB : ('af, active stream) sock * Word8ArraySlice.slice -> int option val recvArrNB' : ('af, active stream) sock * Word8ArraySlice.slice * in_flags -> int option val sendVecTo : ('af, dgram) sock * 'af sock_addr * Word8VectorSlice.slice -> unit val sendArrTo : ('af, dgram) sock * 'af sock_addr * Word8ArraySlice.slice -> unit val sendVecTo' : ('af, dgram) sock * 'af sock_addr * Word8VectorSlice.slice * out_flags -> unit val sendArrTo' : ('af, dgram) sock * 'af sock_addr * Word8ArraySlice.slice * out_flags -> unit val sendVecToNB : ('af, dgram) sock * 'af sock_addr * Word8VectorSlice.slice -> bool val sendVecToNB' : ('af, dgram) sock * 'af sock_addr * Word8VectorSlice.slice * out_flags -> bool val sendArrToNB : ('af, dgram) sock * 'af sock_addr * Word8ArraySlice.slice -> bool val sendArrToNB' : ('af, dgram) sock * 'af sock_addr * Word8ArraySlice.slice * out_flags -> bool val recvVecFrom : ('af, dgram) sock * int -> Word8Vector.vector * 'sock_type sock_addr val recvVecFrom' : ('af, dgram) sock * int * in_flags -> Word8Vector.vector * 'sock_type sock_addr val recvArrFrom : ('af, dgram) sock * Word8ArraySlice.slice -> int * 'af sock_addr val recvArrFrom' : ('af, dgram) sock * Word8ArraySlice.slice * in_flags -> int * 'af sock_addr val recvVecFromNB : ('af, dgram) sock * int -> (Word8Vector.vector * 'sock_type sock_addr) option val recvVecFromNB' : ('af, dgram) sock * int * in_flags -> (Word8Vector.vector * 'sock_type sock_addr) option val recvArrFromNB : ('af, dgram) sock * Word8ArraySlice.slice -> (int * 'af sock_addr) option val recvArrFromNB' : ('af, dgram) sock * Word8ArraySlice.slice * in_flags -> (int * 'af sock_addr) option

Description

type ('af,'sock_type) sock

The type of a socket. Sockets are polymorphic over both the address family and the socket type. The type parameter 'af is instantiated with the appropriate address family type (INetSock.inet or UnixSock.unix). The type parameter 'sock_type is instantiated with the appropriate socket type (dgram or stream).

type 'af sock_addr

The type of a socket address. The type parameter 'af describes the address family of the address (INetSock.inet or UnixSock.unix).

type dgram

The witness type for datagram sockets.

type 'mode stream

The witness type for stream sockets. The type parameter 'mode describes the mode of the stream socket: active or passive.

structure AF

The AF substructure defines an abstract type that represents the different network-address families.

val list : unit -> (string * addr_family) list: This returns a list of all the available address families. Every element of the list is a pair (name,af) where name is the name of the address family, and af is the actual address family value.
The names of the address families are taken from the symbolic constants used in the C Socket API and stripping the leading ``AF_.'' For example, the Unix-domain address family is named "UNIX", the Internet-domain address family is named "INET", and the Apple Talk address family is named "APPLETALK".
val toString : addr_family -> string val fromString : string -> addr_family option: These convert between address family values and their names. For example, the expression toString (INetSock.inetAF) returns the string "INET". fromString returns NONE if no family value corresponds to the given name.
If a pair (name,af) is in the list returned by list, then it is the case that name is equal to toString(af).

structure SOCK

The SOCK substructure provides an abstract type and operations for the different types of sockets. This type is used by the getTYPE function.

eqtype sock_type: The type of socket types.
val stream : sock_type: The stream socket type value.
val dgram : sock_type: The datagram socket type value.
val list : unit -> (string * sock_type) list: A list of the available socket types. Every element of the list is of the form (name,sty) where name is the name of the socket type, and sty is the actual socket type value.
The list of possible socket type names includes "STREAM" for stream sockets, "DGRAM" for datagram sockets, and "RAW" for raw sockets. These names are formed by taking the symbolic constants from the C API and removing the leading ``SOCK_.''
val toString : sock_type -> string val fromString : string -> sock_type option: These convert between a socket type value and its name (e.g., "STREAM"). fromString returns NONE if no socket type value corresponds to the name.
If a pair (name,sty) is in the list returned by list, then it is the case that name is equal to toString(sty).

structure Ctl

The Ctl substructure provides support for manipulating the options associated with a socket. These functions raise the SysErr exception when the argument socket has been closed.

val getDEBUG : ('af, 'sock_type) sock -> bool val setDEBUG : ('af, 'sock_type) sock * bool -> unit: These functions query and set the SO_DEBUG flag for the socket. This flag enables or disables low-level debugging within the kernel. Enabled, it allows the kernel to maintain a history of the recent packets that have been received or sent.
val getREUSEADDR : ('af, 'sock_type) sock -> bool val setREUSEADDR : ('af, 'sock_type) sock * bool -> unit: These query and set the SO_REUSEADDR flag for the socket. When true, this flag instructs the system to allow reuse of local socket addresses in bind calls.
val getKEEPALIVE : ('af, 'sock_type) sock -> bool val setKEEPALIVE : ('af, 'sock_type) sock * bool -> unit: These query and set the SO_KEEPALIVE flag for the socket. When true, the system will generate periodic transmissions on a connected socket, when no other data is being exchanged.
val getDONTROUTE : ('af, 'sock_type) sock -> bool val setDONTROUTE : ('af, 'sock_type) sock * bool -> unit: These query and set the SO_DONTROUTE flag for the socket. When this flag is true, outgoing messages bypass the normal routing mechanisms of the underlying protocol, and are instead directed to the appropriate network interface as specified by the network portion of the destination address. Note that this option can be specified on a per message basis by using one of the sendVec', sendArr', sendVecTo', or sendArrTo' functions.
val getLINGER : ('af, 'sock_type) sock -> Time.time option val setLINGER : ('af, 'sock_type) sock * Time.time option -> unit: These functions query and set the SO_LINGER flag for the socket sock. This flag controls the action taken when unsent messages are queued on socket and a close is performed. If the flag is set to NONE, then the system will close the socket as quickly as possible, discarding data if necessary. If the flag is set to SOME(t) and the socket promises reliable delivery, then the system will block the close operation until the data is delivered or the timeout t expires. If t is negative or too large, then the Time is raised.
val getBROADCAST : ('af, 'sock_type) sock -> bool val setBROADCAST : ('af, 'sock_type) sock * bool -> unit: These query and set the SO_BROADCAST flag for the socket sock, which enables or disables the ability of the process to send broadcast messages over the socket.
val getOOBINLINE : ('af, 'sock_type) sock -> bool val setOOBINLINE : ('af, 'sock_type) sock * bool -> unit: These query and set the SO_OOBINLINE flag for the socket. When set, this indicates that out-of-band data should be placed in the normal input queue of the socket. Note that this option can be specified on a per message basis by using one of the sendVec', sendArr', sendVecTo', or sendArrTo' functions.
val getSNDBUF : ('af, 'sock_type) sock -> int val setSNDBUF : ('af, 'sock_type) sock * int -> unit: These query and set the size of the send queue buffer for the socket.
val getRCVBUF : ('af, 'sock_type) sock -> int val setRCVBUF : ('af, 'sock_type) sock * int -> unit: These query and set the size of receive queue buffer for the socket.
val getTYPE : ('af, 'sock_type) sock -> SOCK.sock_type: This returns the socket type of the socket.
val getERROR : ('af, 'sock_type) sock -> bool: This indicates whether or not an error has occurred.
val getPeerName : ('af, 'sock_type) sock -> 'af sock_addr: This returns the socket address to which the socket is connected.
val getSockName : ('af, 'sock_type) sock -> 'af sock_addr: This returns the socket address to which the socket is bound.
val getNREAD : ('af, 'sock_type) sock -> int: This returns the number of bytes available for reading on the socket.
val getATMARK : ('af, active stream) sock -> bool: This indicates whether or not the read pointer on the socket is currently at the out-of-band mark.

val sameAddr : 'af sock_addr * 'af sock_addr -> bool

This tests whether two socket addresses are the same address.

familyOfAddr addr

returns the address family of the socket address addr.

bind (sock, sa)

binds the address sa to the passive socket sock. This function raises SysErr when the address sa is already in use, when sock is already bound to an address, or when sock has been closed.

listen (sock, n)

creates a queue (of size n) for pending questions associated to the socket sock. The size of queue is limited by the underlying system, but requesting a queue size larger than the limit does not cause an error (a typical limit is 128, but older systems use a limit of 5).

This function raises the SysErr exception if sock has been closed.

accept sock

extracts the first connection request from the queue of pending connections for the socket sock. The socket must have been bound to an address via bind and enabled for listening via listen. If a connection is present, accept returns a pair (s,sa) consisting of a new active socket s with the same properties as sock and the address sa of the connecting entity. If no pending connections are present on the queue then accept blocks until a connection is requested. One can test for pending connection requests by using the select function to test the socket for reading.

This function raises the SysErr exception if sock has not been properly bound and enabled, or it sock has been closed.

val acceptNB : ('af, passive stream) sock -> (('af, active stream) sock * 'af sock_addr) option

This function is the nonblocking form of the accept operation. If the operation can complete without blocking (i.e., there is a pending connection), then this function returns SOME(s,sa), where s is a new active socket with the same properties as sock and sa is the the address of the connecting entity. If there are no pending connections, then this function returns NONE.

This function raises the SysErr exception if sock has not been properly bound and enabled, or it sock has been closed.

connect (sock, sa)

attempts to connect the socket sock to the address sa. If sock is a datagram socket, the address specifies the peer with which the socket is to be associated; sa is the address to which datagrams are to be sent, and the only address from which datagrams are to be received. If sock is a stream socket, the address specifies another socket to which to connect.

This function raises the SysErr exception when the address specified by sa is unreachable, when the connection is refused or times out, when sock is already connected, or when sock has been closed.

val connectNB : ('af, 'sock_type) sock * 'af sock_addr -> bool

This function is the nonblocking form of connect. If the connection can be established without blocking the caller (which is typically true for datagram sockets, but not stream sockets), then true is returned. Otherwise, false is returned and the connection attempt is started; one can test for the completion of the connection by testing the socket for writing using the select function. This function will raise SysErr if it is called on a socket for which a previous connection attempt has not yet been completed.

close sock

closes the connection to the socket sock. This function raises the SysErr exception if the socket has already been closed.

shutdown (sock, mode)

shuts down all or part of a full-duplex connection on socket sock. If mode is NO_RECVS, further receives will be disallowed. If mode is NO_SENDS, further sends will be disallowed. If mode is NO_RECVS_OR_SENDS, further sends and receives will be disallowed. This function raises the SysErr exception if the socket is not connected or has been closed.

type sock_desc

This type is an abstract name for a socket, which is used to support polling on collections of sockets.

sockDesc sock

returns a socket descriptor that names the socket sock.

sameDesc (sd1, sd2)

returns true if the two socket descriptors sd1 and sd2 describe the same underlying socket. Thus, the expression sameDesc(sockDesc sock, sockDesc sock) will always return true for any socket sock.

select {rds, wrs, exs, timeout}

examines the sockets in rds, wrs, and exs to see if they are ready for reading, writing, or have an exceptional condition pending, respectively. The calling program is blocked until either one or more of the named sockets is ``ready '' or the specified timeout expires (where a timeout of NONE never expires). The result of select is a record of three lists of socket descriptors containing the ready sockets from the corresponding argument lists. The order in which socket descriptors appear in the argument lists is preserved in the result lists. A timeout is signified by a result of three empty lists.

This function raises SysErr if any of the argument sockets have been closed or if the timeout value is negative.

Note that one can test if a call to accept will block by using select to see if the socket is ready to read. Similarly, one can use select to test if a call to connect will block by seeing if the socket is ready to write.

ioDesc sock

returns the I/O descriptor corresponding to socket sock. This descriptor can be used to poll the socket via pollDesc and poll in the OS.IO structure. Using the polling mechanism from OS.IO has the advantage that different kinds of I/O objects can be mixed, but not all systems support polling on sockets this way. If an application is only polling sockets, then it is more portable to use the select function defined above.

type out_flags = {don't_route : bool, oob : bool}

Flags used in the general form of socket output operations.

type in_flags = {peek : bool, oob : bool}

Flags used in the general form of socket input operations.

sendVec (sock, slice)

sendArr (sock, slice)

These functions send the bytes in the slice slice on the active stream socket sock. They return the number of bytes actually sent.

These functions raise SysErr if sock has been closed.

sendVec' (sock, slice, {don't_route, oob})

sendArr' (sock, slice, {don't_route, oob})

These functions send the bytes in the slice slice on the active stream socket sock. They return the number of bytes actually sent. If the don't_route flag is true, the data is sent bypassing the normal routing mechanism of the protocol. If oob is true, the data is sent out-of-band, that is, before any other data which may have been buffered.

These functions raise SysErr if sock has been closed.

val sendVecNB : ('af, active stream) sock * Word8VectorSlice.slice -> int option val sendVecNB' : ('af, active stream) sock * Word8VectorSlice.slice * out_flags -> int option val sendArrNB : ('af, active stream) sock * Word8ArraySlice.slice -> int option val sendArrNB' : ('af, active stream) sock * Word8ArraySlice.slice * out_flags -> int option

These functions are the nonblocking versions of sendVec, sendVec', sendArr, and sendArr' (resp.). They have the same semantics as their blocking forms, with the exception that when the operation can complete without blocking, then the result is wrapped in SOME and if the operation would have to wait to send the data, then NONE is returned instead.

recvVec (sock, n)

recvVec'(sock, n, {peek,oob})

These functions receive up to n bytes from the active stream socket sock. The size of the resulting vector is the number of bytes that were successfully received, which may be less than n. If the connection has been closed at the other end (or if n is 0), then the empty vector will be returned.

In the second version, if peek is true, the data is received but not discarded from the connection. If oob is true, the data is received out-of-band, that is, before any other incoming data that may have been buffered.

These functions raise SysErr if the socket sock has been closed and they raise Size if n < 0 or n > Word8Vector.maxLen.

recvArr (sock, slice)

recvArr' (sock, slice, {peek, oob})

These functions read data from the socket sock into the array slice slice. They return the number of bytes actually received. If the connection has been closed at the other end or the slice is empty, then 0 is returned.

For recvArr', if peek is true, the data is received but not discarded from the connection. If oob is true, the data is received out-of-band, that is, before any other incoming data that may have been buffered.

These functions raise SysErr if sock has been closed.

val recvVecNB : ('af, active stream) sock * int -> Word8Vector.vector option val recvVecNB' : ('af, active stream) sock * int * in_flags -> Word8Vector.vector option val recvArrNB : ('af, active stream) sock * Word8ArraySlice.slice -> int option val recvArrNB' : ('af, active stream) sock * Word8ArraySlice.slice * in_flags -> int option

These functions are the nonblocking versions of recvVec, recvVec', recvArr, and recvArr' (resp.). They have the same semantics as their blocking forms, with the exception that when the operation can complete without blocking, then the result is wrapped in SOME and if the operation would have to wait for input, then NONE is returned instead.

sendVecTo (sock, sa, slice)

sendArrTo (sock, sa, slice)

These functions send the message specified by the slice slice on the datagram socket sock to the address sa.

These functions raise SysErr if sock has been closed or if the socket has been connected to a different address than sa.

sendVecTo' (sock, sa, slice, {don't_route, oob})

sendArrTo' (sock, sa, slice, {don't_route, oob})

These functions send the message specified by the slice slice on the datagram socket sock to the address

If the don't_route flag is true, the data is sent bypassing the normal routing mechanism of the protocol. If oob is true, the data is sent out-of-band, that is, before any other data which may have been buffered.

These functions raise SysErr if sock has been closed or if the socket has been connected to a different address than sa.

val sendVecToNB : ('af, dgram) sock * 'af sock_addr * Word8VectorSlice.slice -> bool val sendVecToNB' : ('af, dgram) sock * 'af sock_addr * Word8VectorSlice.slice * out_flags -> bool val sendArrToNB : ('af, dgram) sock * 'af sock_addr * Word8ArraySlice.slice -> bool val sendArrToNB' : ('af, dgram) sock * 'af sock_addr * Word8ArraySlice.slice * out_flags -> bool

These functions are the nonblocking versions of sendVecTo, sendVecTo', sendArrTo, and sendArrTo' (resp.). They have the same semantics as their blocking forms, with the exception that if the operation can complete without blocking, then the operation is performed and true is returned. Otherwise, false is returned and the message is not sent.

recvVecFrom (sock, n)

recvVecFrom' (sock, n, {peek, oob})

These functions receive up to n bytes on the datagram socket sock, and return a pair (vec,sa), where the vector vec is the received message, and sa is the socket address from the which the data originated. If the message is larger than n, then data may be lost.

In the second form, if peek is true, the data is received but not discarded from the connection. If oob is true, the data is received out-of-band, that is, before any other incoming data that may have been buffered.

These functions raise SysErr if sock has been closed; they raise Size if n < 0 or n > Word8Vector.maxLen.

recvArrFrom (sock, slice)

recvArrFrom' (sock, slice)

These functions read a message from the datagram socket sock into the array slice slice. If the message is larger than the size of the slice, then data may be lost. They return the number of bytes actually received. If the connection has been closed at the other end or the slice is empty, then 0 is returned.

For recvArrFrom', if peek is true, the data is received but not discarded from the connection. If oob is true, the data is received out-of-band, that is, before any other incoming data that may have been buffered.

These functions raise SysErr if sock has been closed.

val recvVecFromNB : ('af, dgram) sock * int -> (Word8Vector.vector * 'sock_type sock_addr) option val recvVecFromNB' : ('af, dgram) sock * int * in_flags -> (Word8Vector.vector * 'sock_type sock_addr) option val recvArrFromNB : ('af, dgram) sock * Word8ArraySlice.slice -> (int * 'af sock_addr) option val recvArrFromNB' : ('af, dgram) sock * Word8ArraySlice.slice * in_flags -> (int * 'af sock_addr) option

These functions are the nonblocking versions of recvVecFrom, recvVecFrom', recvArrFrom, and recvArrFrom' (resp.). They have the same semantics as their blocking forms, with the exception that when the operation can complete without blocking, then the result is wrapped in SOME and if the operation would have to wait for input, then NONE is returned instead.

Discussion

Implementation note:

On Unix systems, the non-blocking mode of socket operations is controlled by changing the socket's state using the setsockopt() system call. Thus, implementing the non-blocking operations in the Socket structure may require tracking the socket's blocking/nonblocking state in the representation of the sock type.

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Generated April 12, 2004
Last Modified June 5, 1998
Comments to John Reppy.

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The Standard ML Basis Library

The Socket structure

Synopsis

Interface

Description

See Also

Discussion

The `Socket` structure