HP-UX Reference (11i v1 05/09) - 2 System Calls (vol 5)

g
getsockopt(2) getsockopt(2)
The parameters optval and optlen specify the value of the option. optval is the address of the data struc-
ture that contains the option value, and optlen is the length of the data structure. The type and value of
the data structure that optval points to depends on the option. For "boolean" options, the value may be
zero (not set) or non-zero (set). The value of other options depends on the purpose of the option. Usually,
neither optval nor optlen may be the NULL address or zero; see individual protocol manual entries for any
exceptions, such as tcp(7P) and ip(7P).
For
setsockopt() , optval and optlen are used to pass information from the application to the system.
optval is the address of a location in memory that contains the option information to be passed to the sys-
tem. The parameter optlen is an integer value that specifies the size, in bytes, of the data structure pointed
to by optval.
For
getsockopt() , optval and optlen are used to pass information from the system to the application.
The parameter optlen is the address of a variable. Before calling
getsockopt() , the application should
set the value of the variable to the maximum size, in bytes, of the data structure pointed to by optval. Nor-
mally, upon return, the variable pointed to by optlen is set to the actual size the data returned in the struc-
ture pointed to by optval, if
getsockopt() returns without error.
The following ‘‘socket’’ level option names (optname) are defined in <
sys/socket.h >. The type of the
variable pointed to by optval is indicated in parentheses. Options for other protocol levels are described in
the individual protocol manual pages, such as tcp(7P) and ip(7P).
SO_ACCEPTCONN (int; boolean ) Returns a non-zero value if socket listening is enabled, oth-
erwise returns a zero value.
SO_BROADCAST (int; boolean; SOCK_DGRAM sockets only) Allows the application to send
messages to a broadcast address. Default: disallowed.
Note, the actual effect of this option is communication domain dependent.
In AF_INET domain, broadcasts are always allowed regardless of the value
set for this option. In AF_UNIX domain, broadcasts are not supported.
For validity in other domains, see individual product manual.
SO_DEBUG (int; boolean; AF_INET SOCK_STREAM sockets only) Enables or disables
the recording of internal debug information. Default: disabled.
SO_DONTROUTE (int; boolean; AF_INET sockets only) Causes outbound messages to
bypass normal routing facilities. Instead, messages are sent through the
appropriate network interface based on the network portion of the destina-
tion address. Default: disabled.
SO_ERROR (int) Returns any pending error on the socket, and clears the error status.
The value returned by SO_ERROR would be the value of errno after the
next socket data transfer system call.
SO_KEEPALIVE (int; boolean; AF_INET SOCK_STREAM sockets only) If enabled, keeps
an otherwise idle TCP connection active. Default: disabled.
SO_LINGER (struct linger; AF_INET SOCK_STREAM sockets only) Controls
whether or not an application "lingers" (waits) if there are untransmitted
data in the send socket buffer when the socket is closed. The data type
struct linger is defined in <sys/socket.h >. Default: dis-
abled, as if l_onoff had been set to zero. (See details below.)
SO_OOBINLINE (int; boolean; AF_INET SOCK_STREAM sockets only) If enabled,
specifies that out-of-band data (TCP "urgent data") should be left "in-line"
among the normal data stream. Otherwise, one byte of out-of-band data is
pulled out of the data stream, and it is accessible only by setting MSG_OOB
in the flags parameter when the application reads the data (see recv(2)).
Default: disabled.
SO_RCVBUF (int) Specifies the maximum size, in bytes, of the receive socket buffer.
For SOCK_DGRAM sockets, the receive buffer size may limit the maximum
size of messages that the socket can receive. Default and maximum
values are
protocol-dependent; see individual protocol manual entries,
such as tcp(7P) (default buffer size: 32768 bytes; maximum buffer size:
1073725440 bytes; maximum buffer size can be lowered using the ndd vari-
able tcp_recv_hiwater_max) and udp(7P) (default buffer size: 2147483647
bytes; maximum buffer size: 2147483647 bytes; udp maximum receive
HP-UX 11i Version 1: September 2005 − 2 − Hewlett-Packard Company Section 2−−117