HP-UX Reference (11i v2 07/12) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

s
socket(7) socket(7)
NAME
socket - interprocess communications
DESCRIPTION
Sockets are communication endpoints that allow processes to communicate either locally or remotely. They
are accessed by means of a set of system calls (see socket(2)).
The following
ioctl() requests are defined in
<sys/ioctl.h> (see ioctl(2)):
FIOSNBIO If the int with the address arg is non-zero, the socket is put into non-blocking mode. Other-
wise, the socket is put into blocking mode. Blocking mode is the default. The
FIONBIO
request is equivalent to the FIOSNBIO request, although using
FIONBIO is not recom-
mended. See accept(2), connect(2), recv(2), and send(2) for an explanation of how non-
blocking mode is used.
FIONREAD For SOCK_STREAM sockets, the number of bytes currently readable from this socket is
returned in the integer with the address arg. For SOCK_DGRAM sockets, the number of
bytes currently readable, plus the size of the sockaddr structure (defined in
<sys/socket.h>
), is returned in the integer with the address arg.
SIOCATMARK For SOCK_STREAM TCP sockets, on return the integer with the address arg is non-zero if
the inbound TCP stream has been read up to where the out-of-band data byte starts. Oth-
erwise, the inbound TCP stream has not yet been read up to where the out-of-band data
byte starts. For sockets other than SOCK_STREAM TCP sockets, on return the integer
with the address arg is always zero.
SIOCSPGRP This request sets the process group or process ID associated with the socket to be the value
of the integer with the address arg. A process group or process ID associated with the
socket in this manner is signaled when the state of the socket changes: SIGURG is
delivered upon the receipt of out-of-band data;
SIGIO is delivered if the socket is asyn-
chronous, as described in FIOASYNC below. If the value of the integer with the address
arg is positive, the signal is sent to the process whose process ID matches the value
specified. If the value is negative, the signal is sent to all the processes that have a process
group equal to the absolute value of the value specified. If the value is zero, no signal is
sent to any process. It is necessary to issue this request with a non-zero integer value to
enable the signal delivery mechanism described above. The default for the process group or
process ID value is zero.
SIOCGPGRP This request returns the process group or process ID associated with the socket in the
integer with the address arg. See the explanation for SIOCSPGRP above for more details
on the meaning of the integer value returned.
FIOASYNC If the integer whose address is arg is non-zero, this request sets the state of the socket as
asynchronous. Otherwise, the socket is put into synchronous mode (the default). Asyn-
chronous mode enables the delivery of the SIGIO signal when either of the following con-
ditions is met.
• New data arrives.
• For connection-oriented protocols, whenever additional outgoing buffer space
becomes available or the connection is established or broken.
The process group or process ID associated with the socket must be non-zero in order for
SIGIO signals to be sent. The signal is delivered according to the semantics of
SIOCSPGRP described above.
The fcntl(2) O_NDELAY and O_NONBLOCK flags (defined in <fcntl.h>) are supported by sockets. If
the O_NONBLOCK flag is set, the socket is put into POSIX-style non-blocking mode. If the O_NDELAY
flag is set, the socket is put into non-blocking mode. Otherwise, the socket is put into blocking mode.
Blocking mode is the default. See accept(2), connect(2), recv(2), and send(2) for an explanation of how these
forms of non-blocking mode are used.
Since the fcntl() O_NONBLOCK and O_NDELAY flags and ioctl() FIOSNBIO requests are sup-
ported, the following clarifies on how these features interact. If the O_NONBLOCK or O_NDELAY flag
has been set, recv() and send() requests behave accordingly, regardless of any FIOSNBIO requests.
If neither the O_NONBLOCK flag nor the O_NDELAY flag has been set, FIOSNBIO requests control the
the behavior of recv() and send().
HP-UX 11i Version 2: December 2007 Update − 1 − Hewlett-Packard Company 169