ACCEPT(2)                                                            ACCEPT(2)


NAME
     accept - accept a connection on a socket

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>

     int accept (int s, struct sockaddr *addr, socklen_t *addrlen);

     #if _XOPEN_SOURCE >= 500
       int accept (int s, struct sockaddr *addr, socklen_t *addrlen);
     #elif _XOPEN_SOURCE < 500
       int accept (int s, struct sockaddr *addr, size_t *addrlen);
     #endif

DESCRIPTION
     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
     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 non-blocking and no pending connections are present
     on the queue, accept returns an error as described below.  The accepted
     socket may not be used to accept more connections.  The original socket s
     remains open.

     If addr is non-zero, it 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. If addr is zero, addrlen is ignored.

     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.

RETURN VALUE
     The call returns -1 on error.  If it succeeds, it returns a non-negative
     integer that is a descriptor for the accepted socket.

ERRORS
     The accept will fail if:

     [EBADF]             The descriptor is invalid.


     [ENOTSOCK]          The descriptor references a file, not a socket.

     [EOPNOTSUPP]        The referenced socket is not of type SOCK_STREAM.

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

     [EWOULDBLOCK]       The socket is marked non-blocking and no connections
                         are present to be accepted.

     [EMFILE]            The per-process descriptor table is full.

     [ENFILE]            The system file table is full.

SEE ALSO
     bind(2), connect(2), listen(2), select(2), socket(2)

NOTES
     ABI-compliant versions of the above call can be obtained from
     libsocket.so.

     When used with a socket of type AF_UNIX, this call does not return a
     valid remote address, unless the remote end was explicitly bound to a
     pathname.

     There are three types of accept functions in n32 and 64 bit C libraries
     for IRIX 6.5.19 and later versions. One is the normal type when
     _XOPEN_SOURCE is not defined; the second is XPG5 type when _XOPEN_SOURCE
     is set to >= 500; and the third is XPG4 type when _XOPEN_SOURCE set to <
     500.  The difference between these functions is in the third argument
     type to accept.  Refer <sys/socket.h> for alternate definitions of
     socklen_t type.

          1. For the normal case when _XOPEN_SOURCE is not defined, third
          argument type, a pointer to a socklen_t type, will be an integer
          pointer and the normal accept is used.
          2. When _XOPEN_SOURCE is set to >= 500, third argument type, a
          pointer to a socklen_t type, will actually be a pointer to an
          u_int32_t type and xpg5 type function will be used.
          3. When _XOPEN_SOURCE is set to < 500, third argument type will be a
          pointer to a size_t type and xpg4 type function will be used.

     XPG5 type function is not supported in o32 C library.
     The XPG5 type accept function is actually defined as a static inline
     function in <sys/socket.h>, and it calls a new function _xpg5_accept
     which is specific to IRIX 6.5.19 and later. Therefore applications that
     call XPG5 type accept should check the existence of the new symbol.

            #include <sys/socket.h>
            #include <optional_sym.h>

            if (_MIPS_SYMBOL_PRESENT(_xpg5_accept)) {


                  accept(s, &addr, &addrlen);
            } else {
                  ...
            }


     Because the static inline function is defined in each source file that
     includes <sys/socket.h>, these static functions will have different
     addresses in any cases that inline expansion is not performed. This may
     cause problems if the address of the function is examined in programs.
     To avoid this problem, use -D_XPG5_ACCEPT_USER_DEFINED compile option to
     disable the static inline definition in <sys/socket.h>, and define a user
     defined function with below definition:

          int *
          accept(int _s, struct sockaddr *_addr, socklen_t *_addrlen)
          {
              return(_xpg5_accept(_s, _addr, _addrlen));
          }


     Use the compile option always, when a user defined XPG5 accept function
     is required.


                                                                        Page 3