socket(5)

NAME

socket − Internet Protocol family

SYNOPSIS

#include <sys/socket.h>

DESCRIPTION

The <sys/socket.h> header defines the unsigned integral type sa_family_t through typedef.

The <sys/socket.h> header defines the sockaddr structure that includes the following members:

sa_family_t	sa_family	/∗ address family ∗/
char	sa_data[]	/∗ socket address (variable-length data) ∗/

The <sys/socket.h> header defines the msghdr structure that includes the following members:

void	∗msg_name	/∗ optional address ∗/
size_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 ∗/
size_t	msg_controllen	/∗ ancillary data buffer len ∗/
int	msg_flags	/∗ flags on received message ∗/

The <sys/socket.h> header defines the cmsghdr structure that includes the following members:

size_t	cmsg_len	/∗ data byte count, including hdr ∗/
int	cmsg_level	/∗ originating protocol ∗/
int	cmsg_type	/∗ protocol-specific type ∗/

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 will be legal values for the level argument to the getsockopt() and setsockopt() functions. The SCM_RIGHTS type is supported for level SOL_SOCKET.

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 returns 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 returns 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 returns 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 defines the linger structure that includes the following members:

int	l_onoff	/∗ indicates whether linger option is enabled ∗/
int	l_linger	/∗ linger time, in seconds ∗/

The <sys/socket.h> header defines the following macros:

SOCK_DGRAM Datagram socket

SOCK_STREAM Byte-stream socket

SOCK_SEQPACKET
Sequenced-packet socket

The <sys/socket.h> header defines 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 defines the following macros: for use as the option_name argument in getsockopt() or setsockopt() calls:

SO_DEBUG Debugging information is being recorded.

SO_ACCEPTCONN
Socket is accepting connections.

SO_BROADCAST Transmission of broadcast messages is supported.

SO_REUSEADDR Reuse of local addresses is supported.

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_SNDBUF Send buffer size.

SO_RCVBUF Receive buffer size.

SO_ERROR Socket error status.

SO_TYPE Socket type.

The <sys/socket.h> header defines the following macros for use as the valid values for the msg_flags field in the msghdr structure, or the flags parameter in recvfrom(), recvmsg(), sendto(), or sendmsg() calls:

MSG_CTRUNC Control data truncated.

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 Wait for complete message.

The <sys/socket.h> header defines the following macros:

AF_UNIX UNIX domain sockets

AF_INET Internet domain sockets

The <sys/socket.h> header defines the following macros:

SHUT_RD Disables further receive operations.

SHUT_WR Disables further send operations.

SHUT_RDWR Disables further send and receive operations.

The following are declared as functions, and may also be defined as macros:

int accept(int socket, struct sockaddr ∗address, size_t ∗address_len);

int bind(int socket, const struct sockaddr ∗address, size_t address_len);

int connect(int socket, const struct sockaddr ∗address, size_t address_len);

int getpeername(int socket, struct sockaddr ∗address, size_t ∗address_len);

int getsockname(int socket, struct sockaddr ∗address, size_t ∗address_len);

int getsockopt(int socket, int level, int option_name, void ∗option_value,

size_t ∗option_len);

int listen(int socket, int backlog);

ssize_t recv(int socket, void ∗buffer, size_t length, int flags);

ssize_t recvfrom(int socket, void ∗buffer, size_t length, int flags,

struct sockaddr ∗address, size_t ∗address_len);

ssize_t recvmsg(int socket, struct msghdr ∗message, int flags);

ssize_t send(int socket, const void ∗message, size_t length, int flags);

ssize_t sendmsg(int socket, const struct msghdr ∗message, int flags);

ssize_t sendto(int socket, const void ∗message, size_t length, int flags,

const struct sockaddr ∗dest_addr, size_t dest_len);

int setsockopt(int socket, int level, int option_name, const void ∗option_value,

size_t option_len);

int shutdown(int socket, int how);

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

int socketpair(int domain, int type, int protocol, int socket_vector[2]);

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socket(5)

NAME

SYNOPSIS

DESCRIPTION

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