accept - accept a connection on a socket
int accept(int s, caddr_t addr, int *addrlen);
The argument s is a socket that has been created with socket and bound to
an address with bind, and that is listening for connections after a call
to listen. accept 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. accept uses the netconfig
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.
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.
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.
accept is used with connection-based socket types, currently with
It is possible to select a socket for the purpose of an accept by
selecting it for read. However, this will only indicate when a connect
indication is pending; it is still necessary to call accept.
accept returns -1 on error. If it succeeds, it returns a non-negative
integer that is a descriptor for the accepted socket.
accept will fail if:
EBADF The descriptor is invalid.
ENOTSOCK The descriptor does not reference a socket.
EOPNOTSUPP The referenced socket is not of type SOCK_STREAM.
EWOULDBLOCK The socket is marked as non-blocking and no
connections are present to be accepted.
EPROTO A protocol error has occurred; for example, the
STREAMS protocol stack has not been initialized.
ENODEV The protocol family and type corresponding to s could
not be found in the netconfig file.
ENOMEM There was insufficient user memory available to
complete the operation.
ENOSR There were insufficient STREAMS resources available
to complete the operation.
bind(3N), connect(3N), listen(3N), socket(3N), netconfig(4).
The type of address structure passed to accept depends on the address
family. UNIX domain sockets (address family AF_UNIX) require a
socketaddr_un structure as defined in sys/un.h; Internet domain sockets
(address family AF_INET) require a sockaddr_in structure as defined in
netinet/in.h. Other address families may require other structures. Use
the structure appropriate to the address family; cast the structure
address to a generic caddr_t in the call to accept and pass the size of
the structure in the addrlen argument.
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