Socket(3) Socket(3)
Socket, sockaddr_in, sockaddr_un, inet_aton, inet_ntoa - load the C
socket.h defines and structure manipulators
use Socket;
$proto = getprotobyname('udp');
socket(Socket_Handle, PF_INET, SOCK_DGRAM, $proto);
$iaddr = gethostbyname('hishost.com');
$port = getservbyname('time', 'udp');
$sin = sockaddr_in($port, $iaddr);
send(Socket_Handle, 0, 0, $sin);
$proto = getprotobyname('tcp');
socket(Socket_Handle, PF_INET, SOCK_STREAM, $proto);
$port = getservbyname('smtp');
$sin = sockaddr_in($port,inet_aton("127.1"));
$sin = sockaddr_in(7,inet_aton("localhost"));
$sin = sockaddr_in(7,INADDR_LOOPBACK);
connect(Socket_Handle,$sin);
($port, $iaddr) = sockaddr_in(getpeername(Socket_Handle));
$peer_host = gethostbyaddr($iaddr, AF_INET);
$peer_addr = inet_ntoa($iaddr);
$proto = getprotobyname('tcp');
socket(Socket_Handle, PF_UNIX, SOCK_STREAM, $proto);
unlink('/tmp/usock');
$sun = sockaddr_un('/tmp/usock');
connect(Socket_Handle,$sun);
This module is just a translation of the C socket.h file. Unlike the old
mechanism of requiring a translated socket.ph file, this uses the h2xs
program (see the Perl source distribution) and your native C compiler.
This means that it has a far more likely chance of getting the numbers
right. This includes all of the commonly used pound-defines like
AF_INET, SOCK_STREAM, etc.
In addition, some structure manipulation functions are available:
inet_aton HOSTNAME
Takes a string giving the name of a host, and translates that to the
4-byte string (structure). Takes arguments of both the
'rtfm.mit.edu' type and '18.181.0.24'. If the host name cannot be
resolved, returns undef. For multi-homed hosts (hosts with more than
one address), the first address found is returned.
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Socket(3) Socket(3)
inet_ntoa IP_ADDRESS
Takes a four byte ip address (as returned by inet_aton()) and
translates it into a string of the form 'd.d.d.d' where the 'd's are
numbers less than 256 (the normal readable four dotted number
notation for internet addresses).
INADDR_ANY
Note: does not return a number, but a packed string.
Returns the 4-byte wildcard ip address which specifies any of the
hosts ip addresses. (A particular machine can have more than one ip
address, each address corresponding to a particular network
interface. This wildcard address allows you to bind to all of them
simultaneously.) Normally equivalent to inet_aton('0.0.0.0').
INADDR_BROADCAST
Note: does not return a number, but a packed string.
Returns the 4-byte 'this-lan' ip broadcast address. This can be
useful for some protocols to solicit information from all servers on
the same LAN cable. Normally equivalent to
inet_aton('255.255.255.255').
INADDR_LOOPBACK
Note - does not return a number.
Returns the 4-byte loopback address. Normally equivalent to
inet_aton('localhost').
INADDR_NONE
Note - does not return a number.
Returns the 4-byte 'invalid' ip address. Normally equivalent to
inet_aton('255.255.255.255').
sockaddr_in PORT, ADDRESS
sockaddr_in SOCKADDR_IN
In an array context, unpacks its SOCKADDR_IN argument and returns an
array consisting of (PORT, ADDRESS). In a scalar context, packs its
(PORT, ADDRESS) arguments as a SOCKADDR_IN and returns it. If this
is confusing, use pack_sockaddr_in() and unpack_sockaddr_in()
explicitly.
pack_sockaddr_in PORT, IP_ADDRESS
Takes two arguments, a port number and a 4 byte IP_ADDRESS (as
returned by inet_aton()). Returns the sockaddr_in structure with
those arguments packed in with AF_INET filled in. For internet
domain sockets, this structure is normally what you need for the
arguments in bind(), connect(), and send(), and is also returned by
getpeername(), getsockname() and recv().
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Socket(3) Socket(3)
unpack_sockaddr_in SOCKADDR_IN
Takes a sockaddr_in structure (as returned by pack_sockaddr_in())
and returns an array of two elements: the port and the 4-byte ipaddress.
Will croak if the structure does not have AF_INET in the
right place.
sockaddr_un PATHNAME
sockaddr_un SOCKADDR_UN
In an array context, unpacks its SOCKADDR_UN argument and returns an
array consisting of (PATHNAME). In a scalar context, packs its
PATHNAME arguments as a SOCKADDR_UN and returns it. If this is
confusing, use pack_sockaddr_un() and unpack_sockaddr_un()
explicitly. These are only supported if your system has <sys/un.h>.
pack_sockaddr_un PATH
Takes one argument, a pathname. Returns the sockaddr_un structure
with that path packed in with AF_UNIX filled in. For unix domain
sockets, this structure is normally what you need for the arguments
in bind(), connect(), and send(), and is also returned by
getpeername(), getsockname() and recv().
unpack_sockaddr_un SOCKADDR_UN
Takes a sockaddr_un structure (as returned by pack_sockaddr_un())
and returns the pathname. Will croak if the structure does not have
AF_UNIX in the right place.
socket(3N) socket(3N)
socket - create an endpoint for communication
#include <sys/types.h>
#include <sys/socket.h>
int socket(int domain, int type, int protocol);
socket creates an endpoint for communication and returns a descriptor.
The domain parameter specifies a communications domain within which
communication will take place; this selects the protocol family which
should be used. The protocol family generally is the same as the address
family for the addresses supplied in later operations on the socket.
These families are defined in the include file sys/socket.h. There must
be an entry in the netconfig(4) file for at least each protocol family
and type required. If protocol has been specified, but no exact match
for the tuplet family, type, protocol is found, then the first entry
containing the specified family and type with zero for protocol will be
used. The currently understood formats are:
PF_UNIX UNIX system internal protocols
PF_INET ARPA Internet protocols
The socket has the indicated type, which specifies the communication
semantics. Currently defined types are:
SOCK_STREAM
SOCK_DGRAM
SOCK_RAW
SOCK_SEQPACKET
SOCK_RDM
A SOCK_STREAM type provides sequenced, reliable, two-way connection-based
byte streams. An out-of-band data transmission mechanism may be
supported. A SOCK_DGRAM socket supports datagrams (connectionless,
unreliable messages of a fixed (typically small) maximum length). A
SOCK_SEQPACKET socket may provide a sequenced, reliable, two-way
connection-based data transmission path for datagrams of fixed maximum
length; a consumer may be required to read an entire packet with each
read system call. This facility is protocol specific, and presently not
implemented for any protocol family. SOCK_RAW sockets provide access to
internal network interfaces. The types SOCK_RAW, which is available only
to a privileged user, and SOCK_RDM, for which no implementation currently
exists, are not described here.
protocol specifies a particular protocol to be used with the socket.
Normally only a single protocol exists to support a particular socket
type within a given protocol family. However, multiple protocols may
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socket(3N) socket(3N)
exist, in which case a particular protocol must be specified in this
manner. The protocol number to use is particular to the "communication
domain" in which communication is to take place. If a protocol is
specified by the caller, then it will be packaged into a socket level
option request and sent to the underlying protocol layers.
Sockets of type SOCK_STREAM are full-duplex byte streams, similar to
pipes. A stream socket must be in a connected state before any data may
be sent or received on it. A connection to another socket is created
with a connect(3N) call. Once connected, data may be transferred using
read(2) and write(2) calls or some variant of the send(3N) and recv(3N)
calls. When a session has been completed, a close(2) may be performed.
Out-of-band data may also be transmitted as described on the send(3N)
manual page and received as described on the recv(3N) manual page.
The communications protocols used to implement a SOCK_STREAM insure that
data is not lost or duplicated. If a piece of data for which the peer
protocol has buffer space cannot be successfully transmitted within a
reasonable length of time, then the connection is considered broken and
calls will indicate an error with -1 returns and with ETIMEDOUT as the
specific code in the global variable errno. The protocols optionally
keep sockets "warm" by forcing transmissions roughly every minute in the
absence of other activity. An error is then indicated if no response can
be elicited on an otherwise idle connection for a extended period (for
instance 5 minutes). A SIGPIPE signal is raised if a process sends on a
broken stream; this causes naive processes, which do not handle the
signal, to exit.
SOCK_SEQPACKET sockets employ the same system calls as SOCK_STREAM
sockets. The only difference is that read calls will return only the
amount of data requested, and any remaining in the arriving packet will
be discarded.
SOCK_DGRAM and SOCK_RAW sockets allow datagrams to be sent to
correspondents named in sendto calls. Datagrams are generally received
with recvfrom, which returns the next datagram with its return address.
An fcntl(2) call can be used to specify a process group to receive a
SIGURG signal when the out-of-band data arrives. It may also enable
non-blocking I/O and asynchronous notification of I/O events with SIGIO
signals.
The operation of sockets is controlled by socket level options. These
options are defined in the file /usr/include/sys/socket.h.
setsockopt A -1 is returned if an error occurs. Otherwise the return value is a
descriptor referencing the socket.
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socket(3N) socket(3N)
The socket() call fails if:
EPROTONOSUPPORT The protocol type or the specified protocol is not
supported within this domain.
EMFILE The per-process descriptor table is full.
EACCESS Permission to create a socket of the specified type
and/or protocol is denied.
ENOMEM Insufficient user memory is available.
ENOSR There were insufficient STREAMS resources available
to complete the operation.
close(2), fcntl(2), ioctl(2), read(2), write(2), accept(3N), bind(3N),
connect(3N), getsockname(3N), getsockopt(3N), listen(3N), recv(3N),
send(3N), shutdown(3N), socketpair(3N)
PPPPaaaaggggeeee 3333 [ Back ]
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