socket.2 (2010 09)

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socket(2) socket(2)

NAME

socket() - create an endpoint for communication

SYNOPSIS

#include <sys/socket.h>

AF_CCITT Only

#include <x25/x25ccittproto.h>

int socket(int af, int type, int protocol);

DESCRIPTION

The socket() system call creates an endpoint for communication and returns a descriptor. The socket

descriptor returned is used in all subsequent socket-related system calls.

The af parameter speciﬁes an address family to be used to interpret addresses in later operations that

specify the socket. These address families are deﬁned in the include ﬁles

and

. The only currently supported address families are:

AF_INET (DARPA Internet addresses)

AF_INET6 (Internet Protocol version 6)

AF_ROUTE (routing messages followed by IPv4 or IPv6 addresses)

AF_UNIX (path names on a local node)

AF_CCITT (CCITT X.25 addresses)

AF_VME_LINK (backplane communications on VMEbus)

The type speciﬁes the semantics of communication for the socket. Currently deﬁned types are:

SOCK_STREAM Sequenced, reliable, two-way-connection-based byte streams.

SOCK_DGRAM Datagrams (connectionless, unreliable messages of a ﬁxed, typically small,

maximum length).

protocol speciﬁes a particular protocol to be used with the socket. Normally, only a single protocol exists

to support a particular socket type using a given address family. However, many protocols may exist, in

which case a particular protocol must be speciﬁed. The protocol number to use depends on the commun-

ication domain in which communication is to take place (see services (4) and protocols (4)). protocol can

be speciﬁed as zero, which causes the system to choose a protocol type to use.

Sockets of type SOCK_STREAM are byte streams similar to pipes, except that they are full-duplex

instead of half-duplex. 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() or accept() call. Once

connected, data can be transferred using some variant of the send() and recv() or the read()

and

write() calls. When a session is complete, use close() or shutdown() calls to terminate the con-

nection.

TCP, the communications protocol used to implement SOCK_STREAM for AF_INET or AF_INET6 sock-

ets, ensures that data is not lost or duplicated. If a peer has buffer space for data and the data cannot be

successfully transmitted within a reasonable length of time, the connection is considered broken and the

recv() call indicates an error with errno set to [ETIMEDOUT]. If SO_KEEPALIVE is set and

the connection has been idle for two hours, the TCP protocol sends "keepalive" packets every 75 seconds

to determine whether the connection is active. These transmissions are not visible to users and cannot be

read by a recv() call. If the remote system does not respond within 10 minutes (after 8 "keepalive"

packets have been sent), the next socket call (recv()) returns an error with errno set to

[ETIMEDOUT]. A SIGPIPE signal is raised if a process sends on a broken stream. This causes naive

processes that do not handle the signal to exit. An end-of-ﬁle condition (zero bytes read) is returned if a

process tries to read on a broken stream.

SOCK_DGRAM sockets allow sending of messages to correspondents named in

send() calls. It is also

possible to receive messages at such a socket with recv().

The operation of sockets is controlled by socket level options set by the

setsockopt() system call

described by the getsockopt (2) manual entry. These options are deﬁned in the ﬁle <sys/socket.h>

and explained in the getsockopt (2) manual entry.

X.25 Only

Socket endpoints for communication over an X.25/9000 link can be in either address family, AF_INET or

AF_CCITT. If the socket is in the AF_INET family, the connection behaves as described above. TCP is

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (4 pages)

PAGE 1
socket(2) socket(2) NAME socket() - create an endpoint for communication SYNOPSIS #include AF_CCITT Only #include int socket(int af, int type, int protocol); DESCRIPTION The socket() system call creates an endpoint for communication and returns a descriptor. The socket descriptor returned is used in all subsequent socket-related system calls. The af parameter specifies an address family to be used to interpret addresses in later operations that specify the socket.
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socket(2) socket(2) used if the socket type is SOCK_STREAM. UDP is used if the socket type is SOCK_DGRAM. In both cases, Internet protocol (IP) and the X.25-to-IP interface module are used. If the socket is in the AF_CCITT address family, only the SOCK_STREAM socket type is supported. Refer to the topic "Comparing X.25 Level 3 Access to IP" in the X.25 Programmer’s Guide for more details on the difference between programmatic access to X.25 via IP and X.25 Level 3.
PAGE 3
socket(2) socket(2) [ESOCKTNOSUPPORT] The specified socket type is not supported in this address family. [ETIMEDOUT] Connection timed out. WARNINGS Not all possible errno values are documented in each socket related manpage due to dependencies from the underlying protocol modules. Refer to the errno (2) manpage for a complete list of error codes.
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(Notes) A (Notes) sA 4 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010