accept(3N) bind(3N) accept − accept a connection on a socket

accept(3N) bind(3N) accept − accept a connection on a socket
accept(3N)
accept(3N)
NAME
bind(3N)
bind(3N)
NAME
accept − accept a connection on a socket
bind − bind a name to a socket
SYNOPSIS
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/socket.h>
int accept(int s, struct sockaddr *addr, int *addrlen);
int bind(int s, const struct sockaddr *name, int namelen);
DESCRIPTION
DESCRIPTION
The argument s is a socket that has been created with socket(3N) and bound to an address with bind(3N),
and that is listening for connections after a call to listen(3N). The accept( ) function extracts the first connection on the queue of pending connections, creates a new socket with the properties of s, and allocates a
new file descriptor, ns, for the socket. If no pending connections are present on the queue and the socket is
not marked as non-blocking, accept( ) blocks the caller until a connection is present. If the socket is
marked as non-blocking and no pending connections are present on the queue, accept( ) returns an error as
described below. The accept( ) function uses the netconfig(4) file to determine the STREAMS device file
name associated with s. This is the device on which the connect indication will be accepted. The accepted
socket, ns, is used to read and write data to and from the socket that connected to ns; it is not used to accept
more connections. The original socket (s) remains open for accepting further connections.
bind( ) assigns a name to an unnamed socket. When a socket is created with socket(3N), it exists in a name
space (address family) but has no name assigned. bind( ) requests that the name pointed to by name be
assigned to the socket.
RETURN VALUES
If the bind is successful, 0 is returned. A return value of −1 indicates an error, which is further specified in
the global errno.
ERRORS
The bind( ) call will fail if:
EACCES
The requested address is protected and the current user has inadequate permission
to access it.
The argument addr is a result parameter that is filled in with the address of the connecting entity as it is
known to the communications layer. The exact format of the addr parameter is determined by the domain
in which the communication occurs.
EADDRINUSE
The specified address is already in use.
EADDRNOTAVAIL
The specified address is not available on the local machine.
The argument addrlen is a value-result parameter. Initially, it contains the amount of space pointed to by
addr; on return it contains the length in bytes of the address returned.
EBADF
s is not a valid descriptor.
The accept( ) function is used with connection-based socket types, currently with SOCK_STREAM.
EINVAL
namelen is not the size of a valid address for the specified address family.
It is possible to select(3C) or poll(2) a socket for the purpose of an accept( ) by selecting or polling it for a
read. However, this will only indicate when a connect indication is pending; it is still necessary to call
accept( ).
EINVAL
The socket is already bound to an address.
RETURN VALUES
ENOSR
There were insufficient STREAMS resources for the operation to complete.
ENOTSOCK
s is a descriptor for a file, not a socket.
The following errors are specific to binding names in the UNIX domain:
The accept( ) function returns −1 on error. If it succeeds, it returns a non-negative integer that is a descriptor for the accepted socket.
EACCES
ERRORS
Search permission is denied for a component of the path prefix of the pathname in
name.
EIO
An I/O error occurred while making the directory entry or allocating the inode.
EBADF
The descriptor is invalid.
EISDIR
A null pathname was specified.
EINTR
The accept attempt was interrupted by the delivery of a signal.
ELOOP
Too many symbolic links were encountered in translating the pathname in name.
EMFILE
The per-process descriptor table is full.
ENOENT
A component of the path prefix of the pathname in name does not exist.
ENODEV
The protocol family and type corresponding to s could not be found in the netconfig file.
ENOTDIR
A component of the path prefix of the pathname in name is not a directory.
EROFS
The inode would reside on a read-only file system.
accept( ) will fail if:
ENOMEM
There was insufficient user memory available to complete the operation.
SEE ALSO
EPROTO
A protocol error has occurred; for example, the STREAMS protocol stack has not
been initialized or the connection has already been released.
NOTES
EWOULDBLOCK
The socket is marked as non-blocking and no connections are present to be
accepted.
unlink(2), socket(3N), attributes(5), socket(5)
Binding a name in the UNIX domain creates a socket in the file system that must be deleted by the caller
when it is no longer needed (using unlink(2)).
The rules used in name binding vary between communication domains.
SEE ALSO
poll(2), bind(3N), connect(3N), listen(3N), select(3C), socket(3N), netconfig(4), attributes(5), socket(5)
16 May 1997
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16 May 1997
1
fdopen(3S)
fdopen(3S)
NAME
IP(7)
Linux Programmer’s Manual
IP(7)
NAME
fdopen − associate a stream with a file descriptor
ip − Linux IPv4 protocol implementation
SYNOPSIS
SYNOPSIS
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
FILE *fdopen(int fildes, const char *mode);
DESCRIPTION
tcp_socket = socket(PF_INET, SOCK_STREAM, 0);
raw_socket = socket(PF_INET, SOCK_RAW, protocol);
udp_socket = socket(PF_INET, SOCK_DGRAM, protocol);
The fdopen( ) function associates a stream with a file descriptor fildes, whose value must be less than 255.
The mode argument is a character string having one of the following values:
r or rb
w or wb
a or ab
r+ or rb+ or r+b
w+ or wb+ or w+b
a+ or ab+ or a+b
DESCRIPTION
open a file for reading
open a file for writing
open a file for writing at end of file
open a file for update (reading and writing)
open a file for update (reading and writing)
open a file for update (reading and writing) at end of file
The programmer’s interface is BSD sockets compatible. For more information on sockets, see socket(7).
The meaning of these flags is exactly as specified in fopen(3S), except that modes beginning with w do not
cause truncation of the file.
The mode of the stream must be allowed by the file access mode of the open file. The file position indicator
associated with the new stream is set to the position indicated by the file offset associated with the file
descriptor.
fdopen( ) will preserve the offset maximum previously set for the open file description corresponding to
fildes.
The error and end-of-file indicators for the stream are cleared. The fdopen( ) function may cause the
st_atime field of the underlying file to be marked for update.
An IP socket is created by calling the socket(2) function as socket(PF_INET, socket_type, protocol).
Valid socket types are SOCK_STREAM to open a tcp(7) socket, SOCK_DGRAM to open a udp(7)
socket, or SOCK_RAW to open a raw(7) socket to access the IP protocol directly. protocol is the IP protocol in the IP header to be received or sent. The only valid values for protocol are 0 and IPPROTO_TCP
for TCP sockets and 0 and IPPROTO_UDP for UDP sockets.
When a process wants to receive new incoming packets or connections, it should bind a socket to a local
interface address using bind(2). Only one IP socket may be bound to any given local (address, port) pair.
When INADDR_ANY is specified in the bind call the socket will be bound to all local interfaces. When
listen(2) or connect(2) are called on a unbound socket the socket is automatically bound to a random free
port with the local address set to INADDR_ANY.
ADDRESS FORMAT
An IP socket address is defined as a combination of an IP interface address and a port number. The basic IP
protocol does not supply port numbers, they are implemented by higher level protocols like tcp(7).
RETURN VALUES
struct sockaddr_in {
sa_family_t
sin_family;
u_int16_t
sin_port;
struct in_addr sin_addr;
};
/* Internet address. */
struct in_addr {
u_int32_t
s_addr;
};
Upon successful completion, fdopen( ) returns a pointer to a stream. Otherwise, a null pointer is returned
and errno is set to indicate the error.
fdopen( ) may fail and not set errno if there are no free stdio streams.
ERRORS
The fdopen( ) function may fail if:
EBADF
The fildes argument is not a valid file descriptor.
EINVAL
The mode argument is not a valid mode.
EMFILE
FOPEN_MAX streams are currently open in the calling process.
EMFILE
STREAM_MAX streams are currently open in the calling process.
/* address family: AF_INET */
/* port in network byte order */
/* internet address */
/* address in network byte order */
sin_family is always set to AF_INET. This is required; in Linux 2.2 most networking functions return
EINVAL when this setting is missing. sin_port contains the port in network byte order. The port numbers
below 1024 are called reserved ports. Only processes with effective user id 0 or the
CAP_NET_BIND_SERVICE capability may bind(2) to these sockets.
ENOMEM Insufficient space to allocate a buffer.
USAGE
STREAM_MAX is the number of streams that one process can have open at one time. If defined, it has the
same value as FOPEN_MAX.
File descriptors are obtained from calls like open(2), dup(2), creat(2) or pipe(2), which open files but do
not return streams. Streams are necessary input for almost all of the Section 3S library routines.
SEE ALSO
sin_addr is the IP host address. The addr member of struct in_addr contains the host interface address in
network order. in_addr should be only accessed using the inet_aton(3), inet_addr(3), inet_makeaddr(3)
library functions or directly with the name resolver (see gethostbyname(3)).
Note that the address and the port are always stored in network order. In particular, this means that you
need to call htons(3) on the number that is assigned to a port. All address/port manipulation functions in
the standard library work in network order.
creat(2), dup(2), open(2), pipe(2), fclose(3S), fopen(3S), attributes(5)
SEE ALSO
sendmsg(2), recvmsg(2), socket(7), netlink(7), tcp(7), udp(7), raw(7), ipfw(7)
30 Dec 1996
1
Linux Man Page
2001-06-19
1
OPENDIR(3)
Linux Programmer’s Manual
OPENDIR(3)
NAME
READDIR(3)
Linux Programmer’s Manual
READDIR(3)
NAME
opendir − open a directory
readdir − read a directory
SYNOPSIS
SYNOPSIS
#include <sys/types.h>
#include <sys/types.h>
#include <dirent.h>
#include <dirent.h>
DIR *opendir(const char *name);
struct dirent *readdir(DIR *dir);
DESCRIPTION
DESCRIPTION
The opendir() function opens a directory stream corresponding to the directory name, and returns a pointer
to the directory stream. The stream is positioned at the first entry in the directory.
The readdir() function returns a pointer to a dirent structure representing the next directory entry in the
directory stream pointed to by dir. It returns NULL on reaching the end-of-file or if an error occurred.
The data returned by readdir() is overwritten by subsequent calls to readdir() for the same directory
stream.
RETURN VALUE
The opendir() function returns a pointer to the directory stream or NULL if an error occurred.
The dirent structure is defined as follows:
ERRORS
EACCES
Permission denied.
struct dirent {
long
d_ino;
/* inode number */
off_t
d_off;
/* offset to the next dirent */
unsigned short d_reclen;
/* length of this record */
unsigned char d_type;
/* type of file */
char
d_name[256]; /* filename */
};
EMFILE
Too many file descriptors in use by process.
ENFILE
Too many files are currently open in the system.
ENOENT
Directory does not exist, or name is an empty string.
RETURN VALUE
The readdir() function returns a pointer to a dirent structure, or NULL if an error occurs or end-of-file is
reached.
ENOMEM
Insufficient memory to complete the operation.
ERRORS
ENOTDIR
name is not a directory.
EBADF
Invalid directory stream descriptor dir.
CONFORMING TO
CONFORMING TO
SVID 3, POSIX, BSD 4.3
SVID 3, POSIX, BSD 4.3
SEE ALSO
According to POSIX, the dirent structure contains a field char d_name[] of unspecified size, with at most
NAME_MAX characters preceding the terminating null character. Use of other fields will harm the portability of your programs.
open(2), readdir(3), closedir(3), rewinddir(3), seekdir(3), telldir(3), scandir(3)
BUGS
Field d_type is not implemented as of libc6 2.1 and will always return DT_UNKNOWN (0).
SEE ALSO
read(2), opendir(3), closedir(3), rewinddir(3), seekdir(3), telldir(3), scandir(3)
1995-06-11
1
1996-04-22
1
socket(3N)
socket(3N)
socket − create an endpoint for communication
SYNOPSIS
cc [ flag . . . ] file . . . −lsocket −lnsl [ library . . . ]
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 remaining in the arriving
packet will be discarded.
#include <sys/types.h>
#include <sys/socket.h>
SOCK_DGRAM and SOCK_RAW sockets allow datagrams to be sent to correspondents named in
int socket(int domain, int type, int protocol);
sendto(3N) calls. Datagrams are generally received with recvfrom(3N), which returns the next datagram
with its return address.
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 which should be used. The protocol family generally is the same as the
address family for the addresses supplied in later operations on the socket. These families are defined in
the include file <sys/socket.h>. There must be an entry in the netconfig(4) file for at least each protocol
family and type required. If protocol has been specified, but no exact match for the tuplet family, type, protocol is found, then the first entry containing the specified family and type with zero for protocol will be
used. The currently understood formats are:
UNIX system internal protocols
PF_INET
ARPA Internet protocols
socket(3N)
activity. An error is then indicated if no response can be elicited on an otherwise idle connection for a
extended period (for instance 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.
NAME
PF_UNIX
socket(3N)
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 may also enable non-blocking I/O and asynchronous notification of I/O events with SIGIO
signals.
The operation of sockets is controlled by socket level options. These options are defined in the file
<sys/socket.h>. setsockopt(3N) and getsockopt(3N) 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
The socket( ) call fails if:
The socket has the indicated type, which specifies the communication semantics. 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-ofband 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 may be required to read an entire packet with each read system call.
This facility is protocol specific, and presently not implemented for any protocol family. SOCK_RAW
sockets provide access to internal network interfaces. The types SOCK_RAW, which is available only to
the super-user, and SOCK_RDM, for which no implementation currently exists, are not described here.
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, multiple 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. If a protocol is specified by the
caller, then it will be packaged into a socket level option request and sent to the underlying protocol layers.
Permission to create a socket of the specified type and/or protocol is denied.
EACCES
EMFILE
The per-process descriptor table is full.
ENOMEM
Insufficient user memory is available.
ENOSR
There were insufficient STREAMS resources available to complete the operation.
EPROTONOSUPPORT
The protocol type or the specified protocol is not supported within this
domain.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE
ATTRIBUTE VALUE
MT-Level
Safe
SEE ALSO
close(2), fcntl(2), ioctl(2), read(2), write(2), accept(3N), bind(3N), connect(3N), getsockname(3N), getsockopt(3N), listen(3N), recv(3N), setsockopt(3N), send(3N), shutdown(3N), socketpair(3N),
attributes(5), in(5), socket(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 may be sent or received on it. A connection to another socket is created
with a connect(3N) call. Once connected, data may be transferred using read(2) and write(2) calls or
some variant of the send(3N) and recv(3N) calls. When a session has been completed, a close(2) may be
performed. Out-of-band data may also be transmitted as described on the send(3N) manual page and
received as described on the recv(3N) manual page.
The communications protocols used to implement a SOCK_STREAM insure 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, then 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
16 May 1997
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16 May 1997
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