Originální popis anglicky:
sys/socket.h - main sockets header
Návod, kniha: POSIX Programmer's Manual
#include <sys/socket.h>
The
<sys/socket.h> header shall define the type
socklen_t,
which is an integer type of width of at least 32 bits; see APPLICATION USAGE.
The
<sys/socket.h> header shall define the unsigned integer type
sa_family_t.
The
<sys/socket.h> header shall define the
sockaddr
structure that includes at least the following members:
sa_family_t sa_family Address family.
char sa_data[] Socket address (variable-length data).
The
sockaddr structure is used to define a socket address which is used
in the
bind(),
connect(),
getpeername(),
getsockname(),
recvfrom(), and
sendto() functions.
The
<sys/socket.h> header shall define the
sockaddr_storage
structure. This structure shall be:
- *
- Large enough to accommodate all supported protocol-specific
address structures
- *
- Aligned at an appropriate boundary so that pointers to it
can be cast as pointers to protocol-specific address structures and used
to access the fields of those structures without alignment problems
The
sockaddr_storage structure shall contain at least the following
members:
When a
sockaddr_storage structure is cast as a
sockaddr structure,
the
ss_family field of the
sockaddr_storage structure shall map
onto the
sa_family field of the
sockaddr structure. When a
sockaddr_storage structure is cast as a protocol-specific address
structure, the
ss_family field shall map onto a field of that structure
that is of type
sa_family_t and that identifies the protocol's address
family.
The
<sys/socket.h> header shall define the
msghdr structure
that includes at least the following members:
void *msg_name Optional address.
socklen_t msg_namelen Size of address.
struct iovec *msg_iov Scatter/gather array.
int msg_iovlen Members in msg_iov.
void *msg_control Ancillary data; see below.
socklen_t msg_controllen Ancillary data buffer len.
int msg_flags Flags on received message.
The
msghdr structure is used to minimize the number of directly supplied
parameters to the
recvmsg() and
sendmsg() functions. This
structure is used as a
value-
result parameter in the
recvmsg() function and
value only for the
sendmsg()
function.
The
iovec structure shall be defined as described in
<sys/uio.h> .
The
<sys/socket.h> header shall define the
cmsghdr structure
that includes at least the following members:
socklen_t cmsg_len Data byte count, including the cmsghdr.
int cmsg_level Originating protocol.
int cmsg_type Protocol-specific type.
The
cmsghdr structure is used for storage of ancillary data object
information.
Ancillary data consists of a sequence of pairs, each consisting of a
cmsghdr structure followed by a data array. The data array contains the
ancillary data message, and the
cmsghdr structure contains descriptive
information that allows an application to correctly parse the data.
The values for
cmsg_level shall be legal values for the
level
argument to the
getsockopt() and
setsockopt() functions. The
system documentation shall specify the
cmsg_type definitions for the
supported protocols.
Ancillary data is also possible at the socket level. The
<sys/socket.h> header defines the following macro for use as the
cmsg_type value when
cmsg_level is SOL_SOCKET:
- SCM_RIGHTS
- Indicates that the data array contains the access rights to
be sent or received.
The
<sys/socket.h> header defines the following macros to gain
access to the data arrays in the ancillary data associated with a message
header:
- CMSG_DATA(cmsg)
-
If the argument is a pointer to a cmsghdr structure, this macro shall
return an unsigned character pointer to the data array associated with the
cmsghdr structure.
- CMSG_NXTHDR(mhdr,cmsg)
-
If the first argument is a pointer to a msghdr structure and the
second argument is a pointer to a cmsghdr structure in the
ancillary data pointed to by the msg_control field of that
msghdr structure, this macro shall return a pointer to the next
cmsghdr structure, or a null pointer if this structure is the last
cmsghdr in the ancillary data.
- CMSG_FIRSTHDR(mhdr)
-
If the argument is a pointer to a msghdr structure, this macro shall
return a pointer to the first cmsghdr structure in the ancillary
data associated with this msghdr structure, or a null pointer if
there is no ancillary data associated with the msghdr structure.
The
<sys/socket.h> header shall define the
linger structure
that includes at least the following members:
int l_onoff Indicates whether linger option is enabled.
int l_linger Linger time, in seconds.
The
<sys/socket.h> header shall define the following macros, with
distinct integer values:
- SOCK_DGRAM
- Datagram socket.
- SOCK_RAW
- Raw Protocol Interface.
- SOCK_SEQPACKET
- Sequenced-packet socket.
- SOCK_STREAM
- Byte-stream socket.
The
<sys/socket.h> header shall define the following macro for use
as the
level argument of
setsockopt() and
getsockopt().
- SOL_SOCKET
- Options to be accessed at socket level, not protocol level.
The
<sys/socket.h> header shall define the following macros, with
distinct integer values, for use as the
option_name argument in
getsockopt() or
setsockopt() calls:
- SO_ACCEPTCONN
- Socket is accepting connections.
- SO_BROADCAST
- Transmission of broadcast messages is supported.
- SO_DEBUG
- Debugging information is being recorded.
- SO_DONTROUTE
- Bypass normal routing.
- SO_ERROR
- Socket error status.
- SO_KEEPALIVE
- Connections are kept alive with periodic messages.
- SO_LINGER
- Socket lingers on close.
- SO_OOBINLINE
- Out-of-band data is transmitted in line.
- SO_RCVBUF
- Receive buffer size.
- SO_RCVLOWAT
- Receive ``low water mark''.
- SO_RCVTIMEO
- Receive timeout.
- SO_REUSEADDR
- Reuse of local addresses is supported.
- SO_SNDBUF
- Send buffer size.
- SO_SNDLOWAT
- Send ``low water mark''.
- SO_SNDTIMEO
- Send timeout.
- SO_TYPE
- Socket type.
The
<sys/socket.h> header shall define the following macro as the
maximum
backlog queue length which may be specified by the
backlog field of the
listen() function:
- SOMAXCONN
- The maximum backlog queue length.
The
<sys/socket.h> header shall define the following macros, with
distinct integer values, for use as the valid values for the
msg_flags
field in the
msghdr structure, or the
flags parameter in
recvfrom(),
recvmsg(),
sendmsg(), or
sendto()
calls:
- MSG_CTRUNC
- Control data truncated.
- MSG_DONTROUTE
- Send without using routing tables.
- MSG_EOR
- Terminates a record (if supported by the protocol).
- MSG_OOB
- Out-of-band data.
- MSG_PEEK
- Leave received data in queue.
- MSG_TRUNC
- Normal data truncated.
- MSG_WAITALL
- Attempt to fill the read buffer.
The
<sys/socket.h> header shall define the following macros, with
distinct integer values:
- AF_INET
- Internet domain sockets for use with IPv4 addresses.
- AF_INET6
- Internet domain sockets for use with IPv6 addresses.
- AF_UNIX
- UNIX domain sockets.
- AF_UNSPEC
- Unspecified.
The
<sys/socket.h> header shall define the following macros, with
distinct integer values:
- SHUT_RD
- Disables further receive operations.
- SHUT_RDWR
- Disables further send and receive operations.
- SHUT_WR
- Disables further send operations.
The following shall be declared as functions and may also be defined as macros.
Function prototypes shall be provided.
int accept(int, struct sockaddr *restrict, socklen_t *restrict);
int bind(int, const struct sockaddr *, socklen_t);
int connect(int, const struct sockaddr *, socklen_t);
int getpeername(int, struct sockaddr *restrict, socklen_t *restrict);
int getsockname(int, struct sockaddr *restrict, socklen_t *restrict);
int getsockopt(int, int, int, void *restrict, socklen_t *restrict);
int listen(int, int);
ssize_t recv(int, void *, size_t, int);
ssize_t recvfrom(int, void *restrict, size_t, int,
struct sockaddr *restrict, socklen_t *restrict);
ssize_t recvmsg(int, struct msghdr *, int);
ssize_t send(int, const void *, size_t, int);
ssize_t sendmsg(int, const struct msghdr *, int);
ssize_t sendto(int, const void *, size_t, int, const struct sockaddr *,
socklen_t);
int setsockopt(int, int, int, const void *, socklen_t);
int shutdown(int, int);
int socket(int, int, int);
int sockatmark(int);
int socketpair(int, int, int, int[2]);
Inclusion of
<sys/socket.h> may also make visible all symbols from
<sys/uio.h>.
The following sections are informative.
To forestall portability problems, it is recommended that applications not use
values larger than 2**31 -1 for the
socklen_t type.
The
sockaddr_storage structure solves the problem of declaring storage
for automatic variables which is both large enough and aligned enough for
storing the socket address data structure of any family. For example, code
with a file descriptor and without the context of the address family can pass
a pointer to a variable of this type, where a pointer to a socket address
structure is expected in calls such as
getpeername(), and determine the
address family by accessing the received content after the call.
The example below illustrates a data structure which aligns on a 64-bit
boundary. An implementation-defined field
_ss_align following
_ss_pad1 is used to force a 64-bit alignment which covers proper
alignment good enough for needs of at least
sockaddr_in6 (IPv6) and
sockaddr_in (IPv4) address data structures. The size of padding field
_ss_pad1 depends on the chosen alignment boundary. The size of padding
field
_ss_pad2 depends on the value of overall size chosen for the
total size of the structure. This size and alignment are represented in the
above example by implementation-defined (not required) constants _SS_MAXSIZE
(chosen value 128) and _SS_ALIGNMENT (with chosen value 8). Constants
_SS_PAD1SIZE (derived value 6) and _SS_PAD2SIZE (derived value 112) are also
for illustration and not required. The implementation-defined definitions and
structure field names above start with an underscore to denote implementation
private name space. Portable code is not expected to access or reference those
fields or constants.
/*
* Desired design of maximum size and alignment.
*/
#define _SS_MAXSIZE 128
/* Implementation-defined maximum size. */
#define _SS_ALIGNSIZE (sizeof(int64_t))
/* Implementation-defined desired alignment. */
/*
* Definitions used for sockaddr_storage structure paddings design.
*/
#define _SS_PAD1SIZE (_SS_ALIGNSIZE - sizeof(sa_family_t))
#define _SS_PAD2SIZE (_SS_MAXSIZE - (sizeof(sa_family_t)+ \
_SS_PAD1SIZE + _SS_ALIGNSIZE))
struct sockaddr_storage {
sa_family_t ss_family; /* Address family. */
/*
* Following fields are implementation-defined.
*/
char _ss_pad1[_SS_PAD1SIZE];
/* 6-byte pad; this is to make implementation-defined
pad up to alignment field that follows explicit in
the data structure. */
int64_t _ss_align; /* Field to force desired structure
storage alignment. */
char _ss_pad2[_SS_PAD2SIZE];
/* 112-byte pad to achieve desired size,
_SS_MAXSIZE value minus size of ss_family
__ss_pad1, __ss_align fields is 112. */
};
None.
None.
<sys/uio.h> , the System Interfaces volume of
IEEE Std 1003.1-2001,
accept(),
bind(),
connect(),
getpeername(),
getsockname(),
getsockopt(),
listen(),
recv(),
recvfrom(),
recvmsg(),
send(),
sendmsg(),
sendto(),
setsockopt(),
shutdown(),
socket(),
socketpair()
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
