1IO::Socket(3pm) Perl Programmers Reference Guide IO::Socket(3pm)
2
6 IO::Socket - Object interface to socket communications
7
9 use IO::Socket;
10
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 "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 "IO::Socket" will export all functions (and constants) defined by
21 Socket.
22
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 NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
33 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 NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
38
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 socket
45 socketpair
46 bind
47 listen
48 accept
49 send
50 recv
51 peername (getpeername)
52 sockname (getsockname)
53 shutdown
54 Some methods take slightly different arguments to those defined in
56 perlfunc in attempt to make the interface more flexible. These are
57 accept([PKG])
59 perform the system call "accept" on the socket and return a new
60 object. The new object will be created in the same class as the
61 listen socket, unless "PKG" is specified. This object can be used
62 to communicate with the client that was trying to connect.
63 In a scalar context the new socket is returned, or undef upon
65 failure. In a list context a two-element array is returned
66 containing the new socket and the peer address; the list will be
67 empty upon failure.
68 The timeout in the [PKG] can be specified as zero to effect a
70 "poll", but you shouldn't do that because a new IO::Select object
71 will be created behind the scenes just to do the single poll. This
72 is horrendously inefficient. Use rather true select() with a zero
73 timeout on the handle, or non-blocking IO.
74 socketpair(DOMAIN, TYPE, PROTOCOL)
76 Call "socketpair" and return a list of two sockets created, or an
77 empty list on failure.
78 Additional methods that are provided are:
80 atmark
82 True if the socket is currently positioned at the urgent data mark,
83 false otherwise.
84 use IO::Socket;
86 my $sock = IO::Socket::INET->new('some_server');
88 $sock->read($data, 1024) until $sock->atmark;
89 Note: this is a reasonably new addition to the family of socket
91 functions, so all systems may not support this yet. If it is
92 unsupported by the system, an attempt to use this method will abort
93 the program.
94 The atmark() functionality is also exportable as sockatmark()
96 function:
97 use IO::Socket 'sockatmark';
99 This allows for a more traditional use of sockatmark() as a
101 procedural socket function. If your system does not support
102 sockatmark(), the "use" declaration will fail at compile time.
103 connected
105 If the socket is in a connected state, the peer address is
106 returned. If the socket is not in a connected state, undef is
107 returned.
108 Note that connected() considers a half-open TCP socket to be "in a
110 connected state". Specifically, connected() does not distinguish
111 between the ESTABLISHED and CLOSE-WAIT TCP states; it returns the
112 peer address, rather than undef, in either case. Thus, in general,
113 connected() cannot be used to reliably learn whether the peer has
114 initiated a graceful shutdown because in most cases (see below) the
115 local TCP state machine remains in CLOSE-WAIT until the local
116 application calls shutdown() or close(); only at that point does
117 connected() return undef.
118 The "in most cases" hedge is because local TCP state machine
120 behavior may depend on the peer's socket options. In particular, if
121 the peer socket has SO_LINGER enabled with a zero timeout, then the
122 peer's close() will generate a RST segment, upon receipt of which
123 the local TCP transitions immediately to CLOSED, and in that state,
124 connected() will return undef.
125 protocol
127 Returns the numerical number for the protocol being used on the
128 socket, if known. If the protocol is unknown, as with an AF_UNIX
129 socket, zero is returned.
130 sockdomain
132 Returns the numerical number for the socket domain type. For
133 example, for an AF_INET socket the value of &AF_INET will be
134 returned.
135 sockopt(OPT [, VAL])
137 Unified method to both set and get options in the SOL_SOCKET level.
138 If called with one argument then getsockopt is called, otherwise
139 setsockopt is called.
140 getsockopt(LEVEL, OPT)
142 Get option associated with the socket. Other levels than SOL_SOCKET
143 may be specified here.
144 setsockopt(LEVEL, OPT, VAL)
146 Set option associated with the socket. Other levels than SOL_SOCKET
147 may be specified here.
148 socktype
150 Returns the numerical number for the socket type. For example, for
151 a SOCK_STREAM socket the value of &SOCK_STREAM will be returned.
152 timeout([VAL])
154 Set or get the timeout value (in seconds) associated with this
155 socket. If called without any arguments then the current setting
156 is returned. If called with an argument the current setting is
157 changed and the previous value returned.
158
160 On some systems, for an IO::Socket object created with new_from_fd(),
161 or created with accept() from such an object, the protocol(),
162 sockdomain() and socktype() methods may return undef.
163
165 Socket, IO::Handle, IO::Socket::INET, IO::Socket::UNIX
166
168 Graham Barr. atmark() by Lincoln Stein. Currently maintained by the
169 Perl Porters. Please report all bugs to <perlbug@perl.org>.
170
172 Copyright (c) 1997-8 Graham Barr <gbarr@pobox.com>. All rights
173 reserved. This program is free software; you can redistribute it
174 and/or modify it under the same terms as Perl itself.
175 The atmark() implementation: Copyright 2001, Lincoln Stein
177 <lstein@cshl.org>. This module is distributed under the same terms as
178 Perl itself. Feel free to use, modify and redistribute it as long as
179 you retain the correct attribution.
180perl v5.28.2 2018-11-01 IO::Socket(3pm)