accept(2)accept(2)NAMEaccept - Accept a new connection on a socket
struct sockaddr *address,
socklen_t *address_len );
[XNS4.0] The definition of the accept() function in XNS4.0 uses a
size_t data type instead of socklen_t data type as specified in XNS5.0
(the previous definition).
[Tru64 UNIX] The following definition of the accept() function does
not conform to current standards and is supported only for compatibil‐
ity (see standards(5)): int accept(
struct sockaddr *address,
int *address_len );
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
accept(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
Specifies a file descriptor for the socket that was created with the
socket() function, has been bound to an address with the bind() func‐
tion, and has issued a successful call to the listen() function.
Points to a sockaddr structure, the format of which is determined by
the domain and by the behavior requested for the socket. The sockaddr
structure is an overlay for a sockaddr_in, sockaddr_un, sockaddr_in6,
or sockaddr_storage structure, depending on which of the supported
address families is active.
[Tru64 UNIX] If the compile-time option _SOCKADDR_LEN is
defined before the sys/socket.h header file is included, the
sockaddr structure takes 4.4BSD behavior, with a field for spec‐
ifying the length of the socket address. Otherwise, the default
4.3BSD sockaddr structure is used, with the length of the socket
address assumed to be 14 bytes or less.
You can specify NULL to indicate that the address of the peer is
If _SOCKADDR_LEN is defined, the 4.3BSD sockaddr structure is
defined with the name osockaddr. Specifies the length of the
sockaddr structure pointed to by the address parameter. If the
address parameter is NULL then this parameter is ignored.
The accept() function extracts the first connection on the queue of
pending connections, creates a new socket with the same properties as
the specified socket, and allocates a new file descriptor for that
If the listen() queue is empty of connection requests, the accept()
function blocks a calling socket of the blocking type until a connec‐
tion is present, or returns an [EWOULDBLOCK] for sockets marked non‐
The accepted socket cannot itself accept more connections. The original
socket remains open and can accept more connections.
[Tru64 UNIX] When compiled in the X/Open UNIX environment or the
POSIX.1g socket environment, calls to the accept() function are inter‐
nally renamed by prepending _E to the function name. When you are
debugging a module that includes the accept() function and for which
_XOPEN_SOURCE_EXTENDED or _POSIX_PII_SOCKET has been defined, use _Eac‐
cept to refer to the accept() call. See standards(5) for further infor‐
Upon successful completion, the accept() function returns the nonnega‐
tive socket descriptor of the accepted socket. Additionally, if the
address parameter was specified then it places the address of the peer
in the sockaddr structure pointed to by the address, and sets the
address_len parameter to the length of address. If the accept() func‐
tion fails, a value of -1 is returned and errno is set to indicate the
If the accept() function fails, errno may be set to one of the follow‐
ing values: The socket parameter is not valid. A connection has been
aborted. The address parameter or address_len parameter is inaccessi‐
ble or cannot be written. The accept() function was interrupted by a
signal that was caught before a valid connection arrived. The socket
is not accepting connections. There are too many open file descrip‐
tors. The maximum number of file descriptors in the system are already
open. Insufficient resources are available in the system to complete
the call. The system was unable to allocate kernel memory to increase
the process descriptor table. The available STREAMS resources were
insufficient for the operation to complete. The socket parameter
refers to a file, not a socket. The referenced socket cannot accept
connections. A protocol error occurred. The socket is marked non‐
blocking, and no connections are present to be accepted.
Functions: bind(2), connect(2), listen(2), socket(2).
Network Programmer's Guide