accept - Accepts a new connection on a socket
int accept (
struct sockaddr *address,
socklen_t *address_len );
[XNS4.0] The definition of the accept() function in XNS4.0 uses a a size_t
data type instead of socklen_t data type as specified in XNS5.0 (the previ-
[Tru64 UNIX] The following definition of the accept() function does not
conform to current standards and is supported only for backward compatibil-
ity (see standards(5)):
int accept (
struct sockaddr *address,
int *address_len );
Interfaces documented on this reference page conform to industry standards
Refer to the standards(5) reference page for more information about indus-
try 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 specifying 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
You can specify NULL to indicate that the address of the peer is not
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 parame-
ter 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 socket.
If the listen() queue is empty of connection requests, the accept() func-
tion blocks a calling socket of the blocking type until a connection is
present, or returns an [EWOULDBLOCK] for sockets marked nonblocking.
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 internally 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 _Eaccept to refer to the accept()
call. See standards(5) for further information.
Upon successful completion, the accept() function returns the nonnegative
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() function fails, a
value of -1 is returned and errno is set to indicate the error.
If the accept() function fails, errno may be set to one of the following
[EBADF] The socket parameter is not valid.
A connection has been aborted.
[EFAULT] The address parameter or address_len parameter is inaccessible or
cannot be written.
[EINTR] The accept() function was interrupted by a signal that was caught
before a valid connection arrived.
[EINVAL] The socket is not accepting connections.
[EMFILE] There are too many open file descriptors.
[ENFILE] The maximum number of file descriptors in the system are already
[ENOBUFS] Insufficient resources are available in the system to complete
[ENOMEM] The system was unable to allocate kernel memory to increase the
process descriptor table.
[ENOSR] The available STREAMS resources were insufficient for the opera-
tion to complete.
The socket parameter refers to a file, not a socket.
The referenced socket cannot accept connections.
[EPROTO] A protocol error occurred.
The socket is marked nonblocking, and no connections are present
to be accepted.
Functions: bind(2), connect(2), listen(2), socket(2).