accept() system call

accept(2)                                                           accept(2)



NAME
  accept -  Accepts a new connection on a socket

SYNOPSIS

  #include <sys/types.h>

  #include <sys/socket.h>

  int accept (

          int socket,
          struct sockaddr *address,
          int *address_len );

PARAMETERS

  socket
       Specifies a socket that was created with the socket() function, has
       been bound to an address with the bind() function, and has issued a
       successful call to the listen() function.

  address
       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, or sockaddr_ns
       structure, depending on which of the supported address families is
       active.  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 less.
       You can specify NULL to indicate that the address of the peer is not
       required.

  If _SOCKADDR_LEN is defined, the 4.3BSD sockaddr structure is defined with
  the name osockaddr.

  address_len
       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.

DESCRIPTION

  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.




RETURN VALUES

  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 parameter, 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.

ERRORS

  If the accept() function fails, errno may be set to one of the following
  values:

  [EINVAL]  The socket is not accepting connections.

  [EBADF]   The socket parameter is not valid.

  [ENOMEM]  The system was unable to allocate kernel memory to increase the
            process descriptor table.

  [ENOTSOCK]
            The socket parameter refers to a file, not a socket.

  [EOPNOTSUPP]
            The referenced socket can not accept connections.

  [EFAULT]  The address parameter is not in a writable part of the user
            address space.

  [EWOULDBLOCK]
            The socket is marked nonblocking, and no connections are present
            to be accepted.

  [EMFILE]  There are too many open file descriptors.

RELATED INFORMATION

  Functions: bind(2), connect(2), listen(2), socket(2) delim off