sigvec

sigvec—BSD software signal facilities

SYPNOSIS

#include <bsd/signal.h>
int sigvec(int sig, struct sigvec *vec, struct sigvec *ovec);

DESCRIPTION

This interface is made obsolete by sigaction(2).

Under Linux, sigvec is #defined to sigaction, and provides at best a rough approximation of the BSD sigvec interface.

SEE ALSO

sigaction(2), signal(2)

Linux 1.3 31 August 1995

socket

socket—Creates an endpoint for communication

SYPNOSIS

#include <sys/types.h>
#include <sys/socket.h>
int socket(int domain,inttype, int protocol);

DESCRIPTION

socket creates an endpoint for communication and returns a descriptor.

The domain parameter specifies a communications domain within which communication will take place; this selects the protocol family that should be used. These families are defined in the include file sys/socket.h. The currently understood formats are

The socket has the indicated type, which specifies the semantics of communication. The currently defined types are

SOCK_STREAM

SOCK_DGRAM

SOCK_RAW

SOCK_SEQPACKET

SOCK_RDM

A SOCK_STREAM type provides sequenced, reliable, two-way connection_based byte streams. An out-of-band data transmission mechanism may be supported. A SOCK_DGRAM socket supports datagrams (connectionless, unreliable messages of a fixed, typically small, maximum length). A SOCK_SEQPACKET socket may provide a sequenced, reliable, two-way connection_based data transmission path for datagrams of fixed maximum length; a consumer might be required to read an entire packet with each read system call. This facility is protocol specific, and presently is implemented only for PF_NS. SOCK_RAW sockets provide

access to internal network protocols and interfaces. The types SOCK_RAW, which is available only to the superuser, and SOCK_RDM, which is planned but not yet implemented, are not described here.

The protocol specifies a particular protocol to be used with the socket. Normally only a single protocol exists to support a particular socket type within a given protocol family. However, it is possible that many protocols may exist, in which case a particular protocol must be specified in this manner. The protocol number to use is particular to the communication domain in which communication is to take place; see protocols(5).

Sockets of type SOCK_STREAM are full-duplex byte streams, similar to pipes. A stream socket must be in a connected state before any data can be sent or received on it. A connection to another socket is created with a connect(2) call. Once connected, data may be transferred using read(2) and write(2) calls or some variant of the send(2) and recv(2) calls. When a session has been completed, a close(2) may be performed. Out-of-band data can also be transmitted as described in send(2) and received as described in recv(2).

The communications protocols used to implement a SOCK_STREAM ensure that data is not lost or duplicated. If a piece of data for which the peer protocol has buffer space cannot be successfully transmitted within a reasonable length of time, the connection is considered broken, and calls will indicate an error with _1 returns and with ETIMEDOUT as the specific code in the global variable errno. The protocols optionally keep sockets warm by forcing transmissions roughly every minute in the absence of other activity. An error is then indicated if no response can be elicited on an otherwise idle connection for a extended period (for example, 5 minutes). A SIGPIPE signal is raised if a process sends on a broken stream; this causes naive processes, which do not handle the signal, to exit.

SOCK_SEQPACKET sockets employ the same system calls as SOCK_STREAM sockets. The only difference is that read(2) calls will return only the amount of data requested, and any that is remaining in the arriving packet will be discarded.

SOCK_DGRAM and SOCK_RAW sockets allow the sending of datagrams to correspondents named in send(2) calls. Datagrams are generally received with recvfrom(2), which returns the next datagram with its return address.

An fcntl(2) call can be used to specify a process group to receive a SIGURG signal when the out-of-band data arrives. It can also enable non-blocking I/O and asynchronous notification of I/O events via SIGIO.

The operation of sockets is controlled by socket-level options. These options are defined in the file sys/socket.h. setsockopt(2) and getsockopt(2) and are used to set and get options, respectively.

RETURN VALUES

A _1 is returned if an error occurs; otherwise, the return value is a descriptor referencing the socket.

ERRORS

HISTORY

The socket function call appeared in BSD 4.2.

SEE ALSO

accept(2), bind(2), connect(2), getprotoent(3), getsockname(2), getsockopt(2), ioctl(2), listen(2), read(2), recv(2), select(2), send(2), shutdown(2), socketpair(2), write(2)

"An Introductory 4.3 BSD Interprocess Communication Tutorial" is reprinted in UNIX Programmer's Supplementary Documents Volume 1

"BSD Interprocess Communication Tutorial" is reprinted in UNIX Programmer's Supplementary Documents Volume 1

BSD Man Page, 24 July 1993