


Socket(3p)       Perl Programmers Reference Guide      Socket(3p)


NAME
       Socket, sockaddr_in, sockaddr_un, inet_aton, inet_ntoa -
       load the C socket.h defines and structure manipulators

SYNOPSIS
           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', 'tcp');
           $sin = sockaddr_in($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);


DESCRIPTION
       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.

       Also, some common socket "newline" constants are provided:
       the constants "CR", "LF", and "CRLF", as well as "$CR",
       "$LF", and "$CRLF", which map to "\015", "\012", and
       "\015\012".  If you do not want to use the literal charac-
       ters in your programs, then use the constants provided
       here.  They are not exported by default, but can be
       imported individually, and with the ":crlf" export tag:

           use Socket qw(:DEFAULT :crlf);

       In addition, some structure manipulation functions are
       available:



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Socket(3p)       Perl Programmers Reference Guide      Socket(3p)


       inet_aton HOSTNAME
           Takes a string giving the name of a host, and trans-
           lates 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.

       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 corre-
           sponding to a particular network interface. This wild-
           card address allows you to bind to all of them simul-
           taneously.)  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 equiva-
           lent 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 a list context, unpacks its SOCKADDR_IN argument
           and returns an array consisting of (PORT, ADDRESS).
           In a scalar context, packs its (PORT, ADDRESS) argu-
           ments as a SOCKADDR_IN and returns it.  If this is
           confusing, use pack_sockaddr_in() and



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Socket(3p)       Perl Programmers Reference Guide      Socket(3p)


           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 argu-
           ments 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 an array of two ele-
           ments: the port and the 4-byte ip-address.  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, 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() explic-
           itly.  These are only supported if your system has
           <sys/un.h>.

       pack_sockaddr_un PATH
           Takes one argument, a pathname. Returns the sock-
           addr_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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