1SETSOCKOPT(3P)             POSIX Programmer's Manual            SETSOCKOPT(3P)
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PROLOG

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.
10

NAME

12       setsockopt — set the socket options
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SYNOPSIS

15       #include <sys/socket.h>
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17       int setsockopt(int socket, int level, int option_name,
18           const void *option_value, socklen_t option_len);
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DESCRIPTION

21       The setsockopt()  function  shall  set  the  option  specified  by  the
22       option_name  argument,  at  the  protocol  level specified by the level
23       argument, to the value pointed to by the option_value argument for  the
24       socket  associated  with  the  file  descriptor specified by the socket
25       argument.
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27       The level argument specifies the protocol level  at  which  the  option
28       resides. To set options at the socket level, specify the level argument
29       as SOL_SOCKET. To set options at other levels, supply  the  appropriate
30       level  identifier for the protocol controlling the option. For example,
31       to indicate that an option is interpreted by the TCP (Transport Control
32       Protocol),  set  level  to IPPROTO_TCP as defined in the <netinet/in.h>
33       header.
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35       The option_name argument specifies a single option to set.  It  can  be
36       one of the socket-level options defined in <sys_socket.h> and described
37       in Section 2.10.16, Use of Options.  If option_name is equal to SO_RCV‐
38       TIMEO  or  SO_SNDTIMEO  and  the  implementation  supports  setting the
39       option, it is unspecified whether the  struct  timeval  pointed  to  by
40       option_value is stored as provided by this function or is rounded up to
41       align with the resolution of the clock being used. If  setsockopt()  is
42       called  with  option_name equal to SO_ACCEPTCONN, SO_ERROR, or SO_TYPE,
43       the behavior is unspecified.
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RETURN VALUE

46       Upon successful completion, setsockopt() shall return 0. Otherwise,  -1
47       shall be returned and errno set to indicate the error.
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ERRORS

50       The setsockopt() function shall fail if:
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52       EBADF  The socket argument is not a valid file descriptor.
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54       EDOM   The  send and receive timeout values are too big to fit into the
55              timeout fields in the socket structure.
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57       EINVAL The specified option is invalid at the specified socket level or
58              the socket has been shut down.
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60       EISCONN
61              The  socket  is already connected, and a specified option cannot
62              be set while the socket is connected.
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64       ENOPROTOOPT
65              The option is not supported by the protocol.
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67       ENOTSOCK
68              The socket argument does not refer to a socket.
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70       The setsockopt() function may fail if:
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72       ENOMEM There was insufficient memory available  for  the  operation  to
73              complete.
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75       ENOBUFS
76              Insufficient  resources  are available in the system to complete
77              the call.
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79       The following sections are informative.
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EXAMPLES

82       None.
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APPLICATION USAGE

85       The setsockopt() function provides  an  application  program  with  the
86       means  to  control socket behavior. An application program can use set‐
87       sockopt() to allocate buffer space, control timeouts, or permit  socket
88       data  broadcasts.  The  <sys/socket.h>  header defines the socket-level
89       options available to setsockopt().
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91       Options may exist at multiple protocol  levels.  The  SO_  options  are
92       always present at the uppermost socket level.
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RATIONALE

95       None.
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FUTURE DIRECTIONS

98       None.
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SEE ALSO

101       Section 2.10, Sockets, bind(), endprotoent(), getsockopt(), socket()
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103       The   Base   Definitions   volume   of   POSIX.1‐2017,  <netinet_in.h>,
104       <sys_socket.h>
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107       Portions of this text are reprinted and reproduced in  electronic  form
108       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
109       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
110       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
111       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
112       event of any discrepancy between this version and the original IEEE and
113       The Open Group Standard, the original IEEE and The Open Group  Standard
114       is  the  referee document. The original Standard can be obtained online
115       at http://www.opengroup.org/unix/online.html .
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117       Any typographical or formatting errors that appear  in  this  page  are
118       most likely to have been introduced during the conversion of the source
119       files to man page format. To report such errors,  see  https://www.ker
120       nel.org/doc/man-pages/reporting_bugs.html .
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124IEEE/The Open Group                  2017                       SETSOCKOPT(3P)
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