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The Standard Perl Library
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7.2.58 Socket - 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);

socket(Socket_Handle, PF_UNIX, SOCK_STREAM, 0);
unlink('/tmp/usock');
$sun = sockaddr_un('/tmp/usock');
bind(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 preprocessor-defined constants like AF_INET, SOCK_STREAM, and so on.

In addition, some structure manipulation functions are available:

inet_aton HOSTNAME

Takes a string giving the name of a host, and translates that to a four-byte, packed string (structure). Takes arguments of both the rtfm.mit.edu and 18.181.0.24 types. If the host name cannot be resolved, returns the undefined value.

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 ds are numbers less than 256 (the normal, readable, dotted-quad notation for Internet addresses).

INADDR_ANY

Note: This function does not return a number, but a packed string. Returns the four-byte wildcard IP address that specifies any of the host's 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_LOOPBACK

Note: does not return a number, but a packed string. Returns the four-byte loopback address. Normally equivalent to inet_aton('localhost').

INADDR_NONE

Note: does not return a number, but a packed string. Returns the four-byte invalid IP address. Normally equivalent to inet_aton('255.255.255.255').

sockaddr_in PORT, ADDRESS

sockaddr_in SOCKADDR_IN

In a list context, unpacks its SOCKADDR_IN argument and returns a list 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 four-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.

unpack_sockaddr_in SOCKADDR_IN

Takes a sockaddr_in structure (as returned by pack_sockaddr_in()) and returns a list of two elements: the port and the four-byte IP address. This function will croak if the structure does not have AF_INET in the right place.

sockaddr_un PATHNAME

sockaddr_un SOCKADDR_UN

In a list context, it unpacks its SOCKADDR_UN argument and returns a list consisting of (PATHNAME). In a scalar context, it packs its PATHNAME argument as a SOCKADDR_UN and returns it. If this is confusing, use pack_sockaddr_un() and unpack_sockaddr_un() explicitly. These functions 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.


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