1SETSOCKOPT(3P) POSIX Programmer's Manual SETSOCKOPT(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 setsockopt - set the socket options
13
15 #include <sys/socket.h>
16 int setsockopt(int socket, int level, int option_name,
18 const void *option_value, socklen_t option_len);
19
22 The setsockopt() function shall set the option specified by the
23 option_name argument, at the protocol level specified by the level
24 argument, to the value pointed to by the option_value argument for the
25 socket associated with the file descriptor specified by the socket
26 argument.
27 The level argument specifies the protocol level at which the option
29 resides. To set options at the socket level, specify the level argument
30 as SOL_SOCKET. To set options at other levels, supply the appropriate
31 level identifier for the protocol controlling the option. For example,
32 to indicate that an option is interpreted by the TCP (Transport Control
33 Protocol), set level to IPPROTO_TCP as defined in the <netinet/in.h>
34 header.
35 The option_name argument specifies a single option to set. The
37 option_name argument and any specified options are passed uninterpreted
38 to the appropriate protocol module for interpretations. The
39 <sys/socket.h> header defines the socket-level options. The options
40 are as follows:
41 SO_DEBUG
43 Turns on recording of debugging information. This option enables
44 or disables debugging in the underlying protocol modules. This
45 option takes an int value. This is a Boolean option.
46 SO_BROADCAST
48 Permits sending of broadcast messages, if this is supported by
49 the protocol. This option takes an int value. This is a Boolean
50 option.
51 SO_REUSEADDR
53 Specifies that the rules used in validating addresses supplied
54 to bind() should allow reuse of local addresses, if this is sup‐
55 ported by the protocol. This option takes an int value. This is
56 a Boolean option.
57 SO_KEEPALIVE
59 Keeps connections active by enabling the periodic transmission
60 of messages, if this is supported by the protocol. This option
61 takes an int value.
62 If the connected socket fails to respond to these messages, the connec‐
64 tion is broken and threads writing to that socket are notified with a
65 SIGPIPE signal. This is a Boolean option.
66 SO_LINGER
68 Lingers on a close() if data is present. This option controls
69 the action taken when unsent messages queue on a socket and
70 close() is performed. If SO_LINGER is set, the system shall
71 block the process during close() until it can transmit the data
72 or until the time expires. If SO_LINGER is not specified, and
73 close() is issued, the system handles the call in a way that
74 allows the process to continue as quickly as possible. This
75 option takes a linger structure, as defined in the
76 <sys/socket.h> header, to specify the state of the option and
77 linger interval.
78 SO_OOBINLINE
80 Leaves received out-of-band data (data marked urgent) inline.
81 This option takes an int value. This is a Boolean option.
82 SO_SNDBUF
84 Sets send buffer size. This option takes an int value.
85 SO_RCVBUF
87 Sets receive buffer size. This option takes an int value.
88 SO_DONTROUTE
90 Requests that outgoing messages bypass the standard routing
91 facilities. The destination shall be on a directly-connected
92 network, and messages are directed to the appropriate network
93 interface according to the destination address. The effect, if
94 any, of this option depends on what protocol is in use. This
95 option takes an int value. This is a Boolean option.
96 SO_RCVLOWAT
98 Sets the minimum number of bytes to process for socket input
99 operations. The default value for SO_RCVLOWAT is 1. If
100 SO_RCVLOWAT is set to a larger value, blocking receive calls
101 normally wait until they have received the smaller of the low
102 water mark value or the requested amount. (They may return less
103 than the low water mark if an error occurs, a signal is caught,
104 or the type of data next in the receive queue is different from
105 that returned; for example, out-of-band data.) This option takes
106 an int value. Note that not all implementations allow this
107 option to be set.
108 SO_RCVTIMEO
110 Sets the timeout value that specifies the maximum amount of time
111 an input function waits until it completes. It accepts a timeval
112 structure with the number of seconds and microseconds specifying
113 the limit on how long to wait for an input operation to com‐
114 plete. If a receive operation has blocked for this much time
115 without receiving additional data, it shall return with a par‐
116 tial count or errno set to [EAGAIN] or [EWOULDBLOCK] if no data
117 is received. The default for this option is zero, which indi‐
118 cates that a receive operation shall not time out. This option
119 takes a timeval structure. Note that not all implementations
120 allow this option to be set.
121 SO_SNDLOWAT
123 Sets the minimum number of bytes to process for socket output
124 operations. Non-blocking output operations shall process no
125 data if flow control does not allow the smaller of the send low
126 water mark value or the entire request to be processed. This
127 option takes an int value. Note that not all implementations
128 allow this option to be set.
129 SO_SNDTIMEO
131 Sets the timeout value specifying the amount of time that an
132 output function blocks because flow control prevents data from
133 being sent. If a send operation has blocked for this time, it
134 shall return with a partial count or with errno set to [EAGAIN]
135 or [EWOULDBLOCK] if no data is sent. The default for this option
136 is zero, which indicates that a send operation shall not time
137 out. This option stores a timeval structure. Note that not all
138 implementations allow this option to be set.
139 For Boolean options, 0 indicates that the option is disabled and 1
142 indicates that the option is enabled.
143 Options at other protocol levels vary in format and name.
145
147 Upon successful completion, setsockopt() shall return 0. Otherwise, -1
148 shall be returned and errno set to indicate the error.
149
151 The setsockopt() function shall fail if:
152 EBADF The socket argument is not a valid file descriptor.
154 EDOM The send and receive timeout values are too big to fit into the
156 timeout fields in the socket structure.
157 EINVAL The specified option is invalid at the specified socket level or
159 the socket has been shut down.
160 EISCONN
162 The socket is already connected, and a specified option cannot
163 be set while the socket is connected.
164 ENOPROTOOPT
166 The option is not supported by the protocol.
168 ENOTSOCK
170 The socket argument does not refer to a socket.
171 The setsockopt() function may fail if:
174 ENOMEM There was insufficient memory available for the operation to
176 complete.
177 ENOBUFS
179 Insufficient resources are available in the system to complete
180 the call.
181 The following sections are informative.
184
186 None.
187
189 The setsockopt() function provides an application program with the
190 means to control socket behavior. An application program can use set‐
191 sockopt() to allocate buffer space, control timeouts, or permit socket
192 data broadcasts. The <sys/socket.h> header defines the socket-level
193 options available to setsockopt().
194 Options may exist at multiple protocol levels. The SO_ options are
196 always present at the uppermost socket level.
197
199 None.
200
202 None.
203
205 Sockets, bind(), endprotoent(), getsockopt(), socket(), the Base Defi‐
206 nitions volume of IEEE Std 1003.1-2001, <netinet/in.h>, <sys/socket.h>
207
209 Portions of this text are reprinted and reproduced in electronic form
210 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
211 -- Portable Operating System Interface (POSIX), The Open Group Base
212 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
213 Electrical and Electronics Engineers, Inc and The Open Group. In the
214 event of any discrepancy between this version and the original IEEE and
215 The Open Group Standard, the original IEEE and The Open Group Standard
216 is the referee document. The original Standard can be obtained online
217 at http://www.opengroup.org/unix/online.html .
218IEEE/The Open Group 2003 SETSOCKOPT(3P)