socket.7 (2010 09)

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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. Oth-

erwise, the socket is put into blocking mode. Blocking mode is the default. The

FION-

BIO request is equivalent to the FIOSNBIO request, although using

FIONBIO is not

recommended. 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 pro-

cess group equal to the absolute value of the value speciﬁed. If the value is zero, no sig-

nal 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 pro-

cess 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

conditions 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 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

PAGE 1
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 (see ioctl (2)): FIOSNBIO If the int with the address arg is non-zero, the socket is put into non-blocking mode. Otherwise, the socket is put into blocking mode. Blocking mode is the default.
PAGE 2
socket(7) socket(7) DEPENDENCIES AF_CCITT Only Only the FIOSNBIO, FIONREAD, SIOCGPGRP, and SIOCSPGRP ioctl() requests are defined for af_ccitt sockets. AUTHOR socket was developed by the University of California, Berkeley. SEE ALSO fcntl(2), getsockopt(2), ioctl(2), socket(2).