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

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

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

NNAAMMEE #

 "Socket" - networking constants and support functions

SSYYNNOOPPSSIISS #

 "Socket" a low-level module used by, among other things, the IO::Socket
 family of modules. The following examples demonstrate some low-level uses
 but a practical program would likely use the higher-level API provided by
 "IO::Socket" or similar instead.

  use Socket qw(PF_INET SOCK_STREAM pack_sockaddr_in inet_aton);

  socket(my $socket, PF_INET, SOCK_STREAM, 0)
      or die "socket: $!";

  my $port = getservbyname "echo", "tcp";
  connect($socket, pack_sockaddr_in($port, inet_aton("localhost")))
      or die "connect: $!";

  print $socket "Hello, world!\n";
  print <$socket>;

 See also the "EXAMPLES" section.

DDEESSCCRRIIPPTTIIOONN #

 This module provides a variety of constants, structure manipulators and
 other functions related to socket-based networking. The values and
 functions provided are useful when used in conjunction with Perl core
 functions such as ssoocckkeett(()), sseettssoocckkoopptt(()) and bbiinndd(()). It also provides
 several other support functions, mostly for dealing with conversions of
 network addresses between human-readable and native binary forms, and for
 hostname resolver operations.

 Some constants and functions are exported by default by this module; but
 for backward-compatibility any recently-added symbols are not exported by
 default and must be requested explicitly. When an import list is provided
 to the "use Socket" line, the default exports are not automatically
 imported. It is therefore best practice to always to explicitly list all
 the symbols required.

 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);

  $sock->print("GET / HTTP/1.0$CRLF");

 The entire ggeettaaddddrriinnffoo(()) subsystem can be exported using the tag
 ":addrinfo"; this exports the ggeettaaddddrriinnffoo(()) and ggeettnnaammeeiinnffoo(()) functions,
 and all the "AI_*", "NI_*", "NIx_*" and "EAI_*" constants.

CCOONNSSTTAANNTTSS #

 In each of the following groups, there may be many more constants
 provided than just the ones given as examples in the section heading. If
 the heading ends "..." then this means there are likely more; the exact
 constants provided will depend on the OS and headers found at compile-
 time.

PPFF__IINNEETT,, PPFF__IINNEETT66,, PPFF__UUNNIIXX,, ...... #

 Protocol family constants to use as the first argument to ssoocckkeett(()) or the
 value of the "SO_DOMAIN" or "SO_FAMILY" socket option.

AAFF__IINNEETT,, AAFF__IINNEETT66,, AAFF__UUNNIIXX,, ...... #

 Address family constants used by the socket address structures, to pass
 to such functions as iinneett__ppttoonn(()) or ggeettaaddddrriinnffoo(()), or are returned by
 such functions as ssoocckkaaddddrr__ffaammiillyy(()).

SSOOCCKK__SSTTRREEAAMM,, SSOOCCKK__DDGGRRAAMM,, SSOOCCKK__RRAAWW,, ...... #

 Socket type constants to use as the second argument to ssoocckkeett(()), or the
 value of the "SO_TYPE" socket option.

SSOOCCKK__NNOONNBBLLOOCCKK.. SSOOCCKK__CCLLOOEEXXEECC #

 Linux-specific shortcuts to specify the "O_NONBLOCK" and "FD_CLOEXEC"
 flags during a socket(2) call.

  socket( my $sockh, PF_INET, SOCK_DGRAM|SOCK_NONBLOCK, 0 )

SSOOLL__SSOOCCKKEETT #

 Socket option level constant for sseettssoocckkoopptt(()) and ggeettssoocckkoopptt(()).

SSOO__AACCCCEEPPTTCCOONNNN,, SSOO__BBRROOAADDCCAASSTT,, SSOO__EERRRROORR,, ...... #

 Socket option name constants for sseettssoocckkoopptt(()) and ggeettssoocckkoopptt(()) at the
 "SOL_SOCKET" level.

IIPP__OOPPTTIIOONNSS,, IIPP__TTOOSS,, IIPP__TTTTLL,, ...... #

 Socket option name constants for IPv4 socket options at the "IPPROTO_IP"
 level.

IIPP__PPMMTTUUDDIISSCC__WWAANNTT,, IIPP__PPMMTTUUDDIISSCC__DDOONNTT,, ...... #

 Socket option value constants for "IP_MTU_DISCOVER" socket option.

IIPPTTOOSS__LLOOWWDDEELLAAYY,, IIPPTTOOSS__TTHHRROOUUGGHHPPUUTT,, IIPPTTOOSS__RREELLIIAABBIILLIITTYY,, ...... #

 Socket option value constants for "IP_TOS" socket option.

MMSSGG__BBCCAASSTT,, MMSSGG__OOOOBB,, MMSSGG__TTRRUUNNCC,, ...... #

 Message flag constants for sseenndd(()) and rreeccvv(()).

SSHHUUTT__RRDD,, SSHHUUTT__RRDDWWRR,, SSHHUUTT__WWRR #

 Direction constants for sshhuuttddoowwnn(()).

IINNAADDDDRR__AANNYY,, IINNAADDDDRR__BBRROOAADDCCAASSTT,, IINNAADDDDRR__LLOOOOPPBBAACCKK,, IINNAADDDDRR__NNOONNEE #

 Constants giving the special "AF_INET" addresses for wildcard, broadcast,
 local loopback, and invalid addresses.

 Normally equivalent to inet_aton('0.0.0.0'),
 inet_aton('255.255.255.255'), inet_aton('localhost') and
 inet_aton('255.255.255.255') respectively.

IIPPPPRROOTTOO__IIPP,, IIPPPPRROOTTOO__IIPPVV66,, IIPPPPRROOTTOO__TTCCPP,, ...... #

 IP protocol constants to use as the third argument to ssoocckkeett(()), the level
 argument to ggeettssoocckkoopptt(()) or sseettssoocckkoopptt(()), or the value of the
 "SO_PROTOCOL" socket option.

TTCCPP__CCOORRKK,, TTCCPP__KKEEEEPPAALLIIVVEE,, TTCCPP__NNOODDEELLAAYY,, ...... #

 Socket option name constants for TCP socket options at the "IPPROTO_TCP"
 level.

IINN66AADDDDRR__AANNYY,, IINN66AADDDDRR__LLOOOOPPBBAACCKK #

 Constants giving the special "AF_INET6" addresses for wildcard and local
 loopback.

 Normally equivalent to inet_pton(AF_INET6, "::") and inet_pton(AF_INET6,
 "::1") respectively.

IIPPVV66__AADDDD__MMEEMMBBEERRSSHHIIPP,, IIPPVV66__MMTTUU,, IIPPVV66__VV66OONNLLYY,, ...... #

 Socket option name constants for IPv6 socket options at the
 "IPPROTO_IPV6" level.

SSTTRRUUCCTTUURREE MMAANNIIPPUULLAATTOORRSS #

 The following functions convert between lists of Perl values and packed
 binary strings representing structures.

$$ffaammiillyy == ssoocckkaaddddrr__ffaammiillyy $$ssoocckkaaddddrr Takes a packed socket address (as returned by ppaacckk__ssoocckkaaddddrr__iinn(()), ppaacckk__ssoocckkaaddddrr__uunn(()) or the perl builtin functions ggeettssoocckknnaammee(()) and ggeettppeeeerrnnaammee(())). Returns the address family tag. This will be one of the “AF_*” constants, such as “AF_INET” for a “sockaddr_in” addresses or “AF_UNIX” for a “sockaddr_un”. It can be used to figure out what unpack to use for a sockaddr of unknown type.

$$ssoocckkaaddddrr == ppaacckk__ssoocckkaaddddrr__iinn $$ppoorrtt,, $$iipp__aaddddrreessss Takes two arguments, a port number and an opaque string (as returned by iinneett__aattoonn(()), or a v-string). Returns the “sockaddr_in” structure with those arguments packed in and “AF_INET” filled in. For Internet domain sockets, this structure is normally what you need for the arguments in bbiinndd(()), ccoonnnneecctt(()), and sseenndd(()).

 An undefined $port argument is taken as zero; an undefined $ip_address is
 considered a fatal error.

(($$ppoorrtt,, $$iipp__aaddddrreessss)) == uunnppaacckk__ssoocckkaaddddrr__iinn $$ssoocckkaaddddrr Takes a “sockaddr_in” structure (as returned by ppaacckk__ssoocckkaaddddrr__iinn(()), ggeettppeeeerrnnaammee(()) or rreeccvv(())). Returns a list of two elements: the port and an opaque string representing the IP address (you can use iinneett__nnttooaa(()) to convert the address to the four-dotted numeric format). Will croak if the structure does not represent an “AF_INET” address.

 In scalar context will return just the IP address.

$$ssoocckkaaddddrr == ssoocckkaaddddrr__iinn $$ppoorrtt,, $$iipp__aaddddrreessss (($$ppoorrtt,, $$iipp__aaddddrreessss)) == ssoocckkaaddddrr__iinn $$ssoocckkaaddddrr A wrapper of ppaacckk__ssoocckkaaddddrr__iinn(()) or uunnppaacckk__ssoocckkaaddddrr__iinn(()). In list context, unpacks its argument and returns a list consisting of the port and IP address. In scalar context, packs its port and IP address arguments as a “sockaddr_in” and returns it.

 Provided largely for legacy compatibility; it is better to use
 ppaacckk__ssoocckkaaddddrr__iinn(()) or uunnppaacckk__ssoocckkaaddddrr__iinn(()) explicitly.

$$ssoocckkaaddddrr == ppaacckk__ssoocckkaaddddrr__iinn66 $$ppoorrtt,, $$iipp66__aaddddrreessss,, [[$$ssccooppee__iidd,, [[$$fflloowwiinnffoo]]]] Takes two to four arguments, a port number, an opaque string (as returned by iinneett__ppttoonn(())), optionally a scope ID number, and optionally a flow label number. Returns the “sockaddr_in6” structure with those arguments packed in and “AF_INET6” filled in. IPv6 equivalent of ppaacckk__ssoocckkaaddddrr__iinn(()).

 An undefined $port argument is taken as zero; an undefined $ip6_address
 is considered a fatal error.

(($$ppoorrtt,, $$iipp66__aaddddrreessss,, $$ssccooppee__iidd,, $$fflloowwiinnffoo)) == uunnppaacckk__ssoocckkaaddddrr__iinn66 $$ssoocckkaaddddrr Takes a “sockaddr_in6” structure. Returns a list of four elements: the port number, an opaque string representing the IPv6 address, the scope ID, and the flow label. (You can use iinneett__nnttoopp(()) to convert the address to the usual string format). Will croak if the structure does not represent an “AF_INET6” address.

 In scalar context will return just the IP address.

$$ssoocckkaaddddrr == ssoocckkaaddddrr__iinn66 $$ppoorrtt,, $$iipp66__aaddddrreessss,, [[$$ssccooppee__iidd,, [[$$fflloowwiinnffoo]]]] (($$ppoorrtt,, $$iipp66__aaddddrreessss,, $$ssccooppee__iidd,, $$fflloowwiinnffoo)) == ssoocckkaaddddrr__iinn66 $$ssoocckkaaddddrr A wrapper of ppaacckk__ssoocckkaaddddrr__iinn66(()) or uunnppaacckk__ssoocckkaaddddrr__iinn66(()). In list context, unpacks its argument according to uunnppaacckk__ssoocckkaaddddrr__iinn66(()). In scalar context, packs its arguments according to ppaacckk__ssoocckkaaddddrr__iinn66(()).

 Provided largely for legacy compatibility; it is better to use
 ppaacckk__ssoocckkaaddddrr__iinn66(()) or uunnppaacckk__ssoocckkaaddddrr__iinn66(()) explicitly.

$$ssoocckkaaddddrr == ppaacckk__ssoocckkaaddddrr__uunn $$ppaatthh Takes one argument, a pathname. Returns the “sockaddr_un” structure with that path packed in with “AF_UNIX” filled in. For “PF_UNIX” sockets, this structure is normally what you need for the arguments in bbiinndd(()), ccoonnnneecctt(()), and sseenndd(()).

(($$ppaatthh)) == uunnppaacckk__ssoocckkaaddddrr__uunn $$ssoocckkaaddddrr Takes a “sockaddr_un” structure (as returned by ppaacckk__ssoocckkaaddddrr__uunn(()), ggeettppeeeerrnnaammee(()) or rreeccvv(())). Returns a list of one element: the pathname. Will croak if the structure does not represent an “AF_UNIX” address.

$$ssoocckkaaddddrr == ssoocckkaaddddrr__uunn $$ppaatthh (($$ppaatthh)) == ssoocckkaaddddrr__uunn $$ssoocckkaaddddrr A wrapper of ppaacckk__ssoocckkaaddddrr__uunn(()) or uunnppaacckk__ssoocckkaaddddrr__uunn(()). In a list context, unpacks its argument and returns a list consisting of the pathname. In a scalar context, packs its pathname as a “sockaddr_un” and returns it.

 Provided largely for legacy compatibility; it is better to use
 ppaacckk__ssoocckkaaddddrr__uunn(()) or uunnppaacckk__ssoocckkaaddddrr__uunn(()) explicitly.

 These are only supported if your system has <_s_y_s_/_u_n_._h>.

$$iipp__mmrreeqq == ppaacckk__iipp__mmrreeqq $$mmuullttiiaaddddrr,, $$iinntteerrffaaccee Takes an IPv4 multicast address and optionally an interface address (or “INADDR_ANY”). Returns the “ip_mreq” structure with those arguments packed in. Suitable for use with the “IP_ADD_MEMBERSHIP” and “IP_DROP_MEMBERSHIP” sockopts.

(($$mmuullttiiaaddddrr,, $$iinntteerrffaaccee)) == uunnppaacckk__iipp__mmrreeqq $$iipp__mmrreeqq Takes an “ip_mreq” structure. Returns a list of two elements; the IPv4 multicast address and interface address.

$$iipp__mmrreeqq__ssoouurrccee == ppaacckk__iipp__mmrreeqq__ssoouurrccee $$mmuullttiiaaddddrr,, $$ssoouurrccee,, $$iinntteerrffaaccee Takes an IPv4 multicast address, source address, and optionally an interface address (or “INADDR_ANY”). Returns the “ip_mreq_source” structure with those arguments packed in. Suitable for use with the “IP_ADD_SOURCE_MEMBERSHIP” and “IP_DROP_SOURCE_MEMBERSHIP” sockopts.

(($$mmuullttiiaaddddrr,, $$ssoouurrccee,, $$iinntteerrffaaccee)) == uunnppaacckk__iipp__mmrreeqq__ssoouurrccee $$iipp__mmrreeqq Takes an “ip_mreq_source” structure. Returns a list of three elements; the IPv4 multicast address, source address and interface address.

$$iippvv66__mmrreeqq == ppaacckk__iippvv66__mmrreeqq $$mmuullttiiaaddddrr66,, $$iiffiinnddeexx Takes an IPv6 multicast address and an interface number. Returns the “ipv6_mreq” structure with those arguments packed in. Suitable for use with the “IPV6_ADD_MEMBERSHIP” and “IPV6_DROP_MEMBERSHIP” sockopts.

(($$mmuullttiiaaddddrr66,, $$iiffiinnddeexx)) == uunnppaacckk__iippvv66__mmrreeqq $$iippvv66__mmrreeqq Takes an “ipv6_mreq” structure. Returns a list of two elements; the IPv6 address and an interface number.

FFUUNNCCTTIIOONNSS #

$$iipp__aaddddrreessss == iinneett__aattoonn $$ssttrriinngg Takes a string giving the name of a host, or a textual representation of an IP address and translates that to an packed binary address structure suitable to pass to ppaacckk__ssoocckkaaddddrr__iinn(()). If passed a hostname that 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 iinneett__aattoonn(()) is 32 bits
 wide, in other words, that it would contain only the IPv4 address in
 network order.

 This IPv4-only function is provided largely for legacy reasons. Newly-
 written code should use ggeettaaddddrriinnffoo(()) or iinneett__ppttoonn(()) instead for IPv6
 support.

$$ssttrriinngg == iinneett__nnttooaa $$iipp__aaddddrreessss Takes a packed binary address structure such as returned by uunnppaacckk__ssoocckkaaddddrr__iinn(()) (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).

 This IPv4-only function is provided largely for legacy reasons. Newly-
 written code should use ggeettnnaammeeiinnffoo(()) or iinneett__nnttoopp(()) instead for IPv6
 support.

$$aaddddrreessss == iinneett__ppttoonn $$ffaammiillyy,, $$ssttrriinngg Takes an address family (such as “AF_INET” or “AF_INET6”) and a string containing a textual representation of an address in that family and translates that to an packed binary address structure.

 See also ggeettaaddddrriinnffoo(()) for a more powerful and flexible function to look
 up socket addresses given hostnames or textual addresses.

$$ssttrriinngg == iinneett__nnttoopp $$ffaammiillyy,, $$aaddddrreessss Takes an address family and a packed binary address structure and translates it into a human-readable textual representation of the address; typically in “d.d.d.d” form for “AF_INET” or “hhhh:hhhh::hhhh” form for “AF_INET6”.

 See also ggeettnnaammeeiinnffoo(()) for a more powerful and flexible function to turn
 socket addresses into human-readable textual representations.

(($$eerrrr,, @@rreessuulltt)) == ggeettaaddddrriinnffoo $$hhoosstt,, $$sseerrvviiccee,, [[$$hhiinnttss]] Given both a hostname and service name, this function attempts to resolve the host name into a list of network addresses, and the service name into a protocol and port number, and then returns a list of address structures suitable to ccoonnnneecctt(()) to it.

 Given just a host name, this function attempts to resolve it to a list of
 network addresses, and then returns a list of address structures giving
 these addresses.

 Given just a service name, this function attempts to resolve it to a
 protocol and port number, and then returns a list of address structures
 that represent it suitable to bbiinndd(()) to. This use should be combined with
 the "AI_PASSIVE" flag; see below.

 Given neither name, it generates an error.

 If present, $hints should be a reference to a hash, where the following
 keys are recognised:

 flags => INT
     A bitfield containing "AI_*" constants; see below.

 family => INT
     Restrict to only generating addresses in this address family

 socktype => INT
     Restrict to only generating addresses of this socket type

 protocol => INT
     Restrict to only generating addresses for this protocol

 The return value will be a list; the first value being an error
 indication, followed by a list of address structures (if no error
 occurred).

 The error value will be a dualvar; comparable to the "EAI_*" error
 constants, or printable as a human-readable error message string. If no
 error occurred it will be zero numerically and an empty string.

 Each value in the results list will be a hash reference containing the
 following fields:

 family => INT
     The address family (e.g. "AF_INET")

 socktype => INT
     The socket type (e.g. "SOCK_STREAM")

 protocol => INT
     The protocol (e.g. "IPPROTO_TCP")

 addr => STRING
     The address in a packed string (such as would be returned by
     ppaacckk__ssoocckkaaddddrr__iinn(()))

 canonname => STRING
     The canonical name for the host if the "AI_CANONNAME" flag was
     provided, or "undef" otherwise. This field will only be present on
     the first returned address.

 The following flag constants are recognised in the $hints hash. Other
 flag constants may exist as provided by the OS.

AI_PASSIVE #

     Indicates that this resolution is for a local bbiinndd(()) for a passive
     (i.e.  listening) socket, rather than an active (i.e. connecting)
     socket.

AI_CANONNAME #

     Indicates that the caller wishes the canonical hostname ("canonname")
     field of the result to be filled in.

AI_NUMERICHOST #

     Indicates that the caller will pass a numeric address, rather than a
     hostname, and that ggeettaaddddrriinnffoo(()) must not perform a resolve operation
     on this name. This flag will prevent a possibly-slow network lookup
     operation, and instead return an error if a hostname is passed.

(($$eerrrr,, $$hhoossttnnaammee,, $$sseerrvviicceennaammee)) == ggeettnnaammeeiinnffoo $$ssoocckkaaddddrr,, [[$$ffllaaggss,, [[$$xxffllaaggss]]]] Given a packed socket address (such as from ggeettssoocckknnaammee(()), ggeettppeeeerrnnaammee(()), or returned by ggeettaaddddrriinnffoo(()) in a “addr” field), returns the hostname and symbolic service name it represents. $flags may be a bitmask of “NI_*” constants, or defaults to 0 if unspecified.

 The return value will be a list; the first value being an error
 condition, followed by the hostname and service name.

 The error value will be a dualvar; comparable to the "EAI_*" error
 constants, or printable as a human-readable error message string. The
 host and service names will be plain strings.

 The following flag constants are recognised as $flags. Other flag
 constants may exist as provided by the OS.

NI_NUMERICHOST #

     Requests that a human-readable string representation of the numeric
     address be returned directly, rather than performing a name resolve
     operation that may convert it into a hostname. This will also avoid
     potentially-blocking network IO.

NI_NUMERICSERV #

     Requests that the port number be returned directly as a number
     representation rather than performing a name resolve operation that
     may convert it into a service name.

NI_NAMEREQD #

     If a name resolve operation fails to provide a name, then this flag
     will cause ggeettnnaammeeiinnffoo(()) to indicate an error, rather than returning
     the numeric representation as a human-readable string.

NI_DGRAM #

     Indicates that the socket address relates to a "SOCK_DGRAM" socket,
     for the services whose name differs between TCP and UDP protocols.

 The following constants may be supplied as $xflags.

 NIx_NOHOST
     Indicates that the caller is not interested in the hostname of the
     result, so it does not have to be converted. "undef" will be returned
     as the hostname.

 NIx_NOSERV
     Indicates that the caller is not interested in the service name of
     the result, so it does not have to be converted. "undef" will be
     returned as the service name.

ggeettaaddddrriinnffoo(()) // ggeettnnaammeeiinnffoo(()) EERRRROORR CCOONNSSTTAANNTTSS The following constants may be returned by ggeettaaddddrriinnffoo(()) or ggeettnnaammeeiinnffoo(()). Others may be provided by the OS.

EAI_AGAIN #

     A temporary failure occurred during name resolution. The operation
     may be successful if it is retried later.

EAI_BADFLAGS #

     The value of the "flags" hint to ggeettaaddddrriinnffoo(()), or the $flags
     parameter to ggeettnnaammeeiinnffoo(()) contains unrecognised flags.

EAI_FAMILY #

     The "family" hint to ggeettaaddddrriinnffoo(()), or the family of the socket
     address passed to ggeettnnaammeeiinnffoo(()) is not supported.

EAI_NODATA #

     The host name supplied to ggeettaaddddrriinnffoo(()) did not provide any usable
     address data.

EAI_NONAME #

     The host name supplied to ggeettaaddddrriinnffoo(()) does not exist, or the
     address supplied to ggeettnnaammeeiinnffoo(()) is not associated with a host name
     and the "NI_NAMEREQD" flag was supplied.

EAI_SERVICE #

     The service name supplied to ggeettaaddddrriinnffoo(()) is not available for the
     socket type given in the $hints.

EEXXAAMMPPLLEESS #

LLooookkuupp ffoorr ccoonnnneecctt(()) The ggeettaaddddrriinnffoo(()) function converts a hostname and a service name into a list of structures, each containing a potential way to ccoonnnneecctt(()) to the named service on the named host.

  use IO::Socket;
  use Socket qw(SOCK_STREAM getaddrinfo);

  my %hints = (socktype => SOCK_STREAM);
  my ($err, @res) = getaddrinfo("localhost", "echo", \%hints);
  die "Cannot getaddrinfo - $err" if $err;

  my $sock;

  foreach my $ai (@res) {
      my $candidate = IO::Socket->new();

      $candidate->socket($ai->{family}, $ai->{socktype}, $ai->{protocol})
          or next;

      $candidate->connect($ai->{addr})
          or next;

      $sock = $candidate;
      last;
  }

  die "Cannot connect to localhost:echo" unless $sock;

  $sock->print("Hello, world!\n");
  print <$sock>;

 Because a list of potential candidates is returned, the "while" loop
 tries each in turn until it finds one that succeeds both the ssoocckkeett(()) and
 ccoonnnneecctt(()) calls.

 This function performs the work of the legacy functions ggeetthhoossttbbyynnaammee(()),
 ggeettsseerrvvbbyynnaammee(()), iinneett__aattoonn(()) and ppaacckk__ssoocckkaaddddrr__iinn(()).

 In practice this logic is better performed by IO::Socket::IP.

MMaakkiinngg aa hhuummaann--rreeaaddaabbllee ssttrriinngg oouutt ooff aann aaddddrreessss The ggeettnnaammeeiinnffoo(()) function converts a socket address, such as returned by ggeettssoocckknnaammee(()) or ggeettppeeeerrnnaammee(()), into a pair of human-readable strings representing the address and service name.

  use IO::Socket::IP;
  use Socket qw(getnameinfo);

  my $server = IO::Socket::IP->new(LocalPort => 12345, Listen => 1) or
      die "Cannot listen - $@";

  my $socket = $server->accept or die "accept: $!";

  my ($err, $hostname, $servicename) = getnameinfo($socket->peername);
  die "Cannot getnameinfo - $err" if $err;

  print "The peer is connected from $hostname\n";

 Since in this example only the hostname was used, the redundant
 conversion of the port number into a service name may be omitted by
 passing the "NIx_NOSERV" flag.

  use Socket qw(getnameinfo NIx_NOSERV);

  my ($err, $hostname) = getnameinfo($socket->peername, 0, NIx_NOSERV);

 This function performs the work of the legacy functions
 uunnppaacckk__ssoocckkaaddddrr__iinn(()), iinneett__nnttooaa(()), ggeetthhoossttbbyyaaddddrr(()) and ggeettsseerrvvbbyyppoorrtt(()).

 In practice this logic is better performed by IO::Socket::IP.

RReessoollvviinngg hhoossttnnaammeess iinnttoo IIPP aaddddrreesssseess To turn a hostname into a human-readable plain IP address use ggeettaaddddrriinnffoo(()) to turn the hostname into a list of socket structures, then ggeettnnaammeeiinnffoo(()) on each one to make it a readable IP address again.

  use Socket qw(:addrinfo SOCK_RAW);

  my ($err, @res) = getaddrinfo($hostname, "", {socktype => SOCK_RAW});
  die "Cannot getaddrinfo - $err" if $err;

  while( my $ai = shift @res ) {
      my ($err, $ipaddr) = getnameinfo($ai->{addr}, NI_NUMERICHOST, NIx_NOSERV);
      die "Cannot getnameinfo - $err" if $err;

      print "$ipaddr\n";
  }

 The "socktype" hint to ggeettaaddddrriinnffoo(()) filters the results to only include
 one socket type and protocol. Without this most OSes return three
 combinations, for "SOCK_STREAM", "SOCK_DGRAM" and "SOCK_RAW", resulting
 in triplicate output of addresses. The "NI_NUMERICHOST" flag to
 ggeettnnaammeeiinnffoo(()) causes it to return a string-formatted plain IP address,
 rather than reverse resolving it back into a hostname.

 This combination performs the work of the legacy functions
 ggeetthhoossttbbyynnaammee(()) and iinneett__nnttooaa(()).

AAcccceessssiinngg ssoocckkeett ooppttiioonnss The many “SO_*” and other constants provide the socket option names for ggeettssoocckkoopptt(()) and sseettssoocckkoopptt(()).

  use IO::Socket::INET;
  use Socket qw(SOL_SOCKET SO_RCVBUF IPPROTO_IP IP_TTL);

  my $socket = IO::Socket::INET->new(LocalPort => 0, Proto => 'udp')
      or die "Cannot create socket: $@";

  $socket->setsockopt(SOL_SOCKET, SO_RCVBUF, 64*1024) or
      die "setsockopt: $!";

  print "Receive buffer is ", $socket->getsockopt(SOL_SOCKET, SO_RCVBUF),
      " bytes\n";

  print "IP TTL is ", $socket->getsockopt(IPPROTO_IP, IP_TTL), "\n";

 As a convenience, IO::Socket's sseettssoocckkoopptt(()) method will convert a number
 into a packed byte buffer, and ggeettssoocckkoopptt(()) will unpack a byte buffer of
 the correct size back into a number.

AAUUTTHHOORR #

 This module was originally maintained in Perl core by the Perl 5 Porters.

 It was extracted to dual-life on CPAN at version 1.95 by Paul Evans
 <leonerd@leonerd.org.uk>

perl v5.36.3 2023-02-15 Socket(3p)