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



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('/var/run/usock');
           $sun = sockaddr_un('/var/run/usock');
           connect(Socket_Handle,$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 char-
       acters 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:

       inet_aton HOSTNAME
           Takes a string giving the name of a host, and translates that to an opaque string (if programming in C,
           struct in_addr). 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.

           For portability do not assume that the result of inet_aton() is 32 bits wide, in other words, that it would
           contain only the IPv4 address in network order.

       inet_ntoa IP_ADDRESS
           Takes a string (an opaque string as returned by inet_aton(), or a v-string representing the four octets of
           the IPv4 address in network order) and translates it into a string of the form 'd.d.d.d' where the 'd's are
           numbers less than 256 (the normal human-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_family SOCKADDR
           Takes a sockaddr structure (as returned by pack_sockaddr_in(), pack_sockaddr_un() or the perl builtin func-
           tions getsockname() and getpeername()) and returns the address family tag.  It will match the constant
           AF_INET for a sockaddr_in and AF_UNIX for a sockaddr_un.  It can be used to figure out what unpacker to use
           for a sockaddr of unknown type.

       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) arguments as a SOCKADDR_IN and returns it.  If this is confus-
           ing, use pack_sockaddr_in() and unpack_sockaddr_in() explicitly.

       pack_sockaddr_in PORT, IP_ADDRESS
           Takes two arguments, a port number and an opaque string, IP_ADDRESS (as returned by inet_aton(), or a
           v-string).  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 an array of two elements: the
           port and an opaque string representing the IP address (you can use inet_ntoa() to convert the address to
           the four-dotted numeric format).  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() 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.



perl v5.8.8                       2001-09-21                         Socket(3)