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# Socket

Perl 5 version 10.1 documentation
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# Socket

- NAME
- SYNOPSIS
- DESCRIPTION

# 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 characters 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 functions 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 confusing, 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.

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