VMS Help TCPIP Services, Programming Interfaces, Sockets API, setsockopt()  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Sets options on a socket.
    The $QIO equivalent is the IO$_SETMODE function.
    Format
      #include  <types.h>
      #include  <socket.h>
      int setsockopt  ( int s, int level, int optname, char *optval,
                      int optlen );

1 - Arguments

 s
    A socket descriptor created by the socket() function.
 level
    The protocol level for which the socket options are to be
    modified. It can have one of the following values:
    SOL_SOCKET         Set the options at the socket level.
    p                  Any protocol number. Set the options for
                       protocol level p. See the IN.H header file
                       for the various IPPROTO values.
 optname
    Interpreted by the protocol specified in level. Options at each
    protocol level are documented with the protocol.
    Refer to:
    o  <REFERENCE>(op_setsock_tab) for a list of socket options
    o  <REFERENCE>(tcp_set_tab_opt) for a list of TCP options
    o  <REFERENCE>(ip_set_tab_opt) for a list of IP options
 optval
    Points to a buffer containing the arguments of the specified
    option.
    All socket-level options other than SO_LINGER should be nonzero
    if the option is to be enabled, or zero if it is to be disabled.
    SO_LINGER uses a linger structure argument defined in the
    SOCKET.H header file. This structure specifies the desired state
    of the option and the linger interval. The option value for the
    SO_LINGER command is the address of a linger structure.
    If the socket promises the reliable delivery of data and l_onoff
    is nonzero, the system blocks the process on the close() attempt
    until it is able to transmit the data or until it decides it is
    unable to deliver the information. A timeout period, called the
    linger interval, is specified in l_linger.
    If l_onoff is set to zero and a close() is issued, the system
    processes the close in a manner that allows the process to
    continue as soon as possible.
 optlen
    An integer specifying the size of the buffer pointed to by
    optval.

2 - Description

    This function manipulates options associated with a socket.
    Options can exist at multiple protocol levels. They are always
    present at the uppermost socket level.
    When manipulating socket options, specify the level at which the
    option resides and the name of the option. To manipulate options
    at the socket level, specify the value of level as SOL_SOCKET. To
    manipulate options at any other level, supply the protocol number
    of the appropriate protocol controlling the option. For example,
    to indicate that an option is to be interpreted by TCP, set the
    value for level argument to the protocol number (IPPROTO_TCP) of
    TCP. See the IN.H header file for the various IPPROTO values.

3 - Return Values

    0                  Successful completion.
    -1                 Error; errno is set to indicate the error.

4 - Errors

    EACCES             The calling process does not have appropriate
                       permissions.
    EBADF              The descriptor is invalid.
    EDOM               The send and receive timeout values are too
                       large to fit in the timeout fields of the
                       socket structure.
    EINVAL             The optlen argument is invalid.
    EISCONN            The socket is already connected; the specified
                       option cannot be set when the socket is in the
                       connected state.
    EFAULT             The optval argument is not in a readable part
                       of the user address space.
    ENOBUFS            The system had insufficient resources to
                       complete the call.
    ENOPROTOOPT        The option is unknown.
    ENOTSOCK           The socket descriptor is invalid.
    EFAULT             The optname argument is invalid.