# setsockopt

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           setsockopt — set the socket options
    


## SYNOPSIS



           #include <sys/socket.h>
    
           int setsockopt(int _socket_ , int _level_ , int _option_name_ ,
               const void *_option_value_ , socklen_t _option_len_);
    


## DESCRIPTION



           The _setsockopt_() function shall set the option specified by the
           _option_name_ argument, at the protocol level specified by the _level_
           argument, to the value pointed to by the _option_value_ argument for
           the socket associated with the file descriptor specified by the
           _socket_ argument.
    
           The _level_ argument specifies the protocol level at which the
           option resides. To set options at the socket level, specify the
           _level_ argument as SOL_SOCKET. To set options at other levels,
           supply the appropriate _level_ identifier for the protocol
           controlling the option. For example, to indicate that an option is
           interpreted by the TCP (Transport Control Protocol), set _level_ to
           IPPROTO_TCP as defined in the _< netinet/in.h>_ header.
    
           The _option_name_ argument specifies a single option to set. It can
           be one of the socket-level options defined in sys_socket.h(0p) and
           described in _Section 2.10.16_ , _Use of Options_.  If _option_name_ is
           equal to SO_RCVTIMEO or SO_SNDTIMEO and the implementation
           supports setting the option, it is unspecified whether the **struct**
           **timeval** pointed to by _option_value_ is stored as provided by this
           function or is rounded up to align with the resolution of the
           clock being used. If _setsockopt_() is called with _option_name_ equal
           to SO_ACCEPTCONN, SO_ERROR, or SO_TYPE, the behavior is
           unspecified.
    


## RETURN VALUE



           Upon successful completion, _setsockopt_() shall return 0.
           Otherwise, -1 shall be returned and _errno_ set to indicate the
           error.
    


## ERRORS



           The _setsockopt_() function shall fail if:
    
           **EBADF** The _socket_ argument is not a valid file descriptor.
    
           **EDOM** The send and receive timeout values are too big to fit into
                  the timeout fields in the socket structure.
    
           **EINVAL** The specified option is invalid at the specified socket
                  level or the socket has been shut down.
    
           **EISCONN**
                  The socket is already connected, and a specified option
                  cannot be set while the socket is connected.
    
           **ENOPROTOOPT**
                  The option is not supported by the protocol.
    
           **ENOTSOCK**
                  The _socket_ argument does not refer to a socket.
    
           The _setsockopt_() function may fail if:
    
           **ENOMEM** There was insufficient memory available for the operation
                  to complete.
    
           **ENOBUFS**
                  Insufficient resources are available in the system to
                  complete the call.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           The _setsockopt_() function provides an application program with the
           means to control socket behavior. An application program can use
           _setsockopt_() to allocate buffer space, control timeouts, or permit
           socket data broadcasts. The _< sys/socket.h>_ header defines the
           socket-level options available to _setsockopt_().
    
           Options may exist at multiple protocol levels. The SO_ options are
           always present at the uppermost socket level.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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