ACCEPT(2) System Calls Manual ACCEPT(2)
accept - accept a connection on a socket
int accept(s, addr, addrlen)
struct sockaddr *addr;
The argument s is a socket that has been created with socket(2), bound
to an address with bind(2), and is listening for connections after a
listen(2). accept() extracts the first connection on the queue of
pending connections, creates a new socket with the same properties of s
and allocates a new file descriptor for the socket. If no pending con-
nections 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 is used to read and write data to and from the
socket which connected to this one; it is not used to accept more con-
nections. The original socket s remains open for accepting further
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 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. This call is used with connection-based socket
types, currently with SOCK_STREAM.
It is possible to select(2) a socket for the purposes of doing an
accept() by selecting it for read.
accept() returns a non-negative descriptor for the accepted socket on
success. On failure, it returns -1 and sets errno to indicate the
EBADF The descriptor is invalid.
EFAULT The addr parameter is not in a writable part of the user
ENOTSOCK The descriptor references a file, not a socket.
EOPNOTSUPP The referenced socket is not of type SOCK_STREAM.
EWOULDBLOCK The socket is marked non-blocking and no connections are
present to be accepted.
bind(2), connect(2), listen(2), select(2), socket(2)
21 January 1990 ACCEPT(2)