1IO::Socket(3pm)        Perl Programmers Reference Guide        IO::Socket(3pm)
2
3
4

NAME

6       IO::Socket - Object interface to socket communications
7

SYNOPSIS

9           use IO::Socket;
10

DESCRIPTION

12       "IO::Socket" provides an object interface to creating and using
13       sockets. It is built upon the IO::Handle interface and inherits all the
14       methods defined by IO::Handle.
15
16       "IO::Socket" only defines methods for those operations which are common
17       to all types of socket. Operations which are specified to a socket in a
18       particular domain have methods defined in sub classes of "IO::Socket"
19
20       "IO::Socket" will export all functions (and constants) defined by
21       Socket.
22

CONSTRUCTOR

24       new ( [ARGS] )
25           Creates an "IO::Socket", which is a reference to a newly created
26           symbol (see the "Symbol" package). "new" optionally takes
27           arguments, these arguments are in key-value pairs.  "new" only
28           looks for one key "Domain" which tells new which domain the socket
29           will be in. All other arguments will be passed to the configuration
30           method of the package for that domain, See below.
31
32           NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
33
34           As of VERSION 1.18 all IO::Socket objects have autoflush turned on
35           by default. This was not the case with earlier releases.
36
37           NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
38

METHODS

40       See perlfunc for complete descriptions of each of the following
41       supported "IO::Socket" methods, which are just front ends for the
42       corresponding built-in functions:
43
44           socket
45           socketpair
46           bind
47           listen
48           accept
49           sockname (getsockname)
50           shutdown
51
52       Some methods take slightly different arguments to those defined in
53       perlfunc in attempt to make the interface more flexible. These are
54
55       accept([PKG])
56           perform the system call "accept" on the socket and return a new
57           object. The new object will be created in the same class as the
58           listen socket, unless "PKG" is specified. This object can be used
59           to communicate with the client that was trying to connect.
60
61           In a scalar context the new socket is returned, or undef upon
62           failure. In a list context a two-element array is returned
63           containing the new socket and the peer address; the list will be
64           empty upon failure.
65
66           The timeout in the [PKG] can be specified as zero to effect a
67           "poll", but you shouldn't do that because a new IO::Select object
68           will be created behind the scenes just to do the single poll.  This
69           is horrendously inefficient.  Use rather true select() with a zero
70           timeout on the handle, or non-blocking IO.
71
72       socketpair(DOMAIN, TYPE, PROTOCOL)
73           Call "socketpair" and return a list of two sockets created, or an
74           empty list on failure.
75
76       Additional methods that are provided are:
77
78       atmark
79           True if the socket is currently positioned at the urgent data mark,
80           false otherwise.
81
82               use IO::Socket;
83
84               my $sock = IO::Socket::INET->new('some_server');
85               $sock->read($data, 1024) until $sock->atmark;
86
87           Note: this is a reasonably new addition to the family of socket
88           functions, so all systems may not support this yet.  If it is
89           unsupported by the system, an attempt to use this method will abort
90           the program.
91
92           The atmark() functionality is also exportable as sockatmark()
93           function:
94
95                   use IO::Socket 'sockatmark';
96
97           This allows for a more traditional use of sockatmark() as a
98           procedural socket function.  If your system does not support
99           sockatmark(), the "use" declaration will fail at compile time.
100
101       connected
102           If the socket is in a connected state, the peer address is
103           returned. If the socket is not in a connected state, undef is
104           returned.
105
106           Note that connected() considers a half-open TCP socket to be "in a
107           connected state".  Specifically, connected() does not distinguish
108           between the ESTABLISHED and CLOSE-WAIT TCP states; it returns the
109           peer address, rather than undef, in either case.  Thus, in general,
110           connected() cannot be used to reliably learn whether the peer has
111           initiated a graceful shutdown because in most cases (see below) the
112           local TCP state machine remains in CLOSE-WAIT until the local
113           application calls shutdown() or close(); only at that point does
114           connected() return undef.
115
116           The "in most cases" hedge is because local TCP state machine
117           behavior may depend on the peer's socket options. In particular, if
118           the peer socket has SO_LINGER enabled with a zero timeout, then the
119           peer's close() will generate a RST segment, upon receipt of which
120           the local TCP transitions immediately to CLOSED, and in that state,
121           connected() will return undef.
122
123       send(MSG, [, FLAGS [, TO ] ])
124           Like the built-in send(), except that:
125
126           ·   "FLAGS" is optional and defaults to 0, and
127
128           ·   after a successful send with "TO", further calls to send() on
129               an unconnected socket without "TO" will send to the same
130               address, and "TO" will be used as the result of peername().
131
132       recv(BUF, LEN, [,FLAGS])
133           Like the built-in recv(), except that:
134
135           ·   "FLAGS" is optional and defaults to 0, and
136
137           ·   the cached value returned by peername() is updated with the
138               result of recv().
139
140       peername
141           Returns the cached peername, possibly set by recv() or send()
142           above.  If not otherwise set returns (and caches) the result of
143           getpeername().
144
145       protocol
146           Returns the numerical number for the protocol being used on the
147           socket, if known. If the protocol is unknown, as with an AF_UNIX
148           socket, zero is returned.
149
150       sockdomain
151           Returns the numerical number for the socket domain type. For
152           example, for an AF_INET socket the value of &AF_INET will be
153           returned.
154
155       sockopt(OPT [, VAL])
156           Unified method to both set and get options in the SOL_SOCKET level.
157           If called with one argument then getsockopt is called, otherwise
158           setsockopt is called.
159
160       getsockopt(LEVEL, OPT)
161           Get option associated with the socket. Other levels than SOL_SOCKET
162           may be specified here.
163
164       setsockopt(LEVEL, OPT, VAL)
165           Set option associated with the socket. Other levels than SOL_SOCKET
166           may be specified here.
167
168       socktype
169           Returns the numerical number for the socket type. For example, for
170           a SOCK_STREAM socket the value of &SOCK_STREAM will be returned.
171
172       timeout([VAL])
173           Set or get the timeout value (in seconds) associated with this
174           socket.  If called without any arguments then the current setting
175           is returned. If called with an argument the current setting is
176           changed and the previous value returned.
177

LIMITATIONS

179       On some systems, for an IO::Socket object created with new_from_fd(),
180       or created with accept() from such an object, the protocol(),
181       sockdomain() and socktype() methods may return undef.
182

SEE ALSO

184       Socket, IO::Handle, IO::Socket::INET, IO::Socket::UNIX
185

AUTHOR

187       Graham Barr.  atmark() by Lincoln Stein.  Currently maintained by the
188       Perl Porters.  Please report all bugs to <perlbug@perl.org>.
189
191       Copyright (c) 1997-8 Graham Barr <gbarr@pobox.com>. All rights
192       reserved.  This program is free software; you can redistribute it
193       and/or modify it under the same terms as Perl itself.
194
195       The atmark() implementation: Copyright 2001, Lincoln Stein
196       <lstein@cshl.org>.  This module is distributed under the same terms as
197       Perl itself.  Feel free to use, modify and redistribute it as long as
198       you retain the correct attribution.
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202perl v5.30.2                      2020-03-27                   IO::Socket(3pm)
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