|ACCEPT(2)||System Calls Manual||ACCEPT(2)|
s, struct sockaddr
s, struct sockaddr
accept() call extracts the first connection request on the queue of pending connections, creates a new socket with the same non-blocking I/O mode as s, and allocates a new file descriptor for the socket with the close-on-exec flag clear.
accept4() system call is similar,
however the non-blocking I/O mode of the new socket is determined by the
SOCK_NONBLOCK flag in the
flags argument and the close-on-exec flag on the new
file descriptor is determined by the
flag in the flags argument.
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 non-blocking
and no pending connections are present on the queue,
accept() returns an error as described below. The
accepted socket may not be used to accept more connections. The original
socket s remains open.
The argument addr is a result parameter that
is filled in with the address of the connecting entity as known to the
communications layer. The exact format of the addr
parameter is determined by the domain in which the communication is
occurring. The structure
sockaddr_storage exists for
greater portability. It is large enough to hold any of the types that may be
returned in the addr parameter.
The addrlen is a value-result parameter; it
should initially contain the amount of space pointed to by
addr; on return it will contain the actual length (in
bytes) of the address returned. If addrlen does not
point to enough space to hold the entire socket address, the result will be
truncated to the initial value of addrlen (in bytes).
This call is used with connection-based socket types, currently with
accept4() return a non-negative integer, the accepted socket file descriptor. Otherwise, a value of -1 is returned and errno is set to indicate the error.
sockaddr_storageto allocate enough space for the returned address:
#include <sys/types.h> #include <sys/socket.h> struct sockaddr_storage addr; socklen_t len = sizeof(addr); int retcode; retcode = accept(s, (struct sockaddr *)&addr, &len); if (retcode == -1) err(1, "accept");
accept4() will fail if:
accept4() will fail if
accept() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”). The
accept4() function is expected to conform to a future revision of that standard.
accept() system call first appeared in 4.1cBSD and
accept4() in OpenBSD 5.7.
ENFILEis returned, new connections are neither dequeued nor discarded. Thus considerable care is required in select(2) and poll(2) loops.
|May 26, 2019||OpenBSD-current|