NAME

accept − accept a connection on a socket

SYNOPSIS

#include <sys/types.h>

int accept(int s, caddr_t addr, int ∗addrlen);

DESCRIPTION

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 SOCK_STREAM. 

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. 

RETURN VALUE

accept returns −1 on error.  If it succeeds, it returns a non-negative integer that is a descriptor for the accepted socket. 

ERRORS

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. 

SEE ALSO

bind(3N), connect(3N), listen(3N), socket(3N), netconfig(4)

NOTES

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.