The argument
.I addr
-is a pointer to a
+is a pointer to a
.I sockaddr
structure.
This structure is filled in with the address of the peer socket,
The exact format of the address returned
.I addr
is determined by the socket's address family (see
-.BR socket (2)
+.BR socket (2)
and the respective protocol man pages).
The
.I addrlen
size of the structure pointed to by
.IR addr ;
on return it will contain the actual length (in bytes) of the address
-returned. When
+returned.
+When
.I addr
is NULL nothing is filled in.
.PP
connections are present on the queue, and the socket is not marked as
non-blocking,
.BR accept ()
-blocks the caller until a connection is present. If the socket is marked
+blocks the caller until a connection is present.
+If the socket is marked
non-blocking and no pending connections are present on the queue,
.BR accept ()
-fails with the error EAGAIN.
+fails with the error EAGAIN.
.PP
In order to be notified of incoming connections on a socket, you can use
.BR select (2)
A readable event will be delivered when a new connection is attempted and you
may then call
.BR accept ()
-to get a socket for that connection. Alternatively, you can set the socket
-to deliver
+to get a socket for that connection.
+Alternatively, you can set the socket to deliver
.B SIGIO
when activity occurs on a socket; see
.BR socket (7)
DECNet,
.BR accept ()
can be thought of as merely dequeuing the next connection request and not
-implying confirmation. Confirmation can be implied by
+implying confirmation.
+Confirmation can be implied by
a normal read or write on the new file descriptor, and rejection can be
-implied by closing the new socket. Currently only
-DECNet
-has these semantics on Linux.
+implied by closing the new socket.
+Currently only
+DECNet
+has these semantics on Linux.
.SH NOTES
There may not always be a connection waiting after a
.B SIGIO
.I errno
is set appropriately.
.SH "ERROR HANDLING"
-Linux
+Linux
.BR accept ()
-passes already-pending network errors on the new socket
-as an error code from
-.BR accept ().
+passes already-pending network errors on the new socket
+as an error code from
+.BR accept ().
This behaviour differs from other BSD socket
-implementations. For reliable operation the application should detect
-the network errors defined for the protocol after
+implementations.
+For reliable operation the application should detect
+the network errors defined for the protocol after
.BR accept ()
and treat
-them like
+them like
.BR EAGAIN
-by retrying. In case of TCP/IP these are
+by retrying.
+In case of TCP/IP these are
.BR ENETDOWN ,
.BR EPROTO ,
.BR ENOPROTOOPT ,
.TP
.B EINTR
The system call was interrupted by a signal that was caught
-before a valid connection arrived.
+before a valid connection arrived.
.TP
.B EINVAL
Socket is not listening for connections, or
.TP
.B EOPNOTSUPP
The referenced socket is not of type
-.BR SOCK_STREAM .
+.BR SOCK_STREAM .
.PP
.BR accept ()
may fail if:
argument is not in a writable part of the user address space.
.TP
.B ENOBUFS, ENOMEM
-Not enough free memory.
+Not enough free memory.
This often means that the memory allocation is limited by the socket buffer
limits, not by the system memory.
.TP
Firewall rules forbid connection.
.PP
In addition, network errors for the new socket and as defined
-for the protocol may be returned. Various Linux kernels can
+for the protocol may be returned.
+Various Linux kernels can
return other errors such as
.BR ENOSR ,
.BR ESOCKTNOSUPPORT ,
.B ERESTARTSYS
may be seen during a trace.
.SH "CONFORMING TO"
-SVr4, 4.4BSD,
+SVr4, 4.4BSD,
.RB ( accept ()
-first appeared in 4.2BSD), POSIX.1-2001.
+first appeared in 4.2BSD), POSIX.1-2001.
.\" The BSD man page documents five possible error returns
.\" (EBADF, ENOTSOCK, EOPNOTSUPP, EWOULDBLOCK, EFAULT).
-.\" POSIX.1-2001 documents errors
+.\" POSIX.1-2001 documents errors
.\" EAGAIN, EBADF, ECONNABORTED, EINTR, EINVAL, EMFILE,
-.\" ENFILE, ENOBUFS, ENOMEM, ENOTSOCK, EOPNOTSUPP, EPROTO, EWOULDBLOCK.
+.\" ENFILE, ENOBUFS, ENOMEM, ENOTSOCK, EOPNOTSUPP, EPROTO, EWOULDBLOCK.
.\" In addition, SUSv2 documents EFAULT and ENOSR.
.LP
On Linux, the new socket returned by
-.BR accept ()
+.BR accept ()
does \fInot\fP inherit file status flags such as
.BR O_NONBLOCK
and
This behaviour differs from the canonical BSD sockets implementation.
.\" Some testing seems to show that Tru64 5.1 and HP-UX 11 also
.\" do not inherit file status flags -- MTK Jun 05
-Portable programs should not rely on inheritance or non-inheritance
-of file status flags and always explicitly set all required flags on
-the socket returned from
+Portable programs should not rely on inheritance or non-inheritance
+of file status flags and always explicitly set all required flags on
+the socket returned from
.BR accept ().
.SH NOTE
The third argument of
.\" .I fails: only italicizes a single line
"_Any_ sane library _must_ have "socklen_t" be the same size
-as int. Anything else breaks any BSD socket layer stuff.
+as int.
+Anything else breaks any BSD socket layer stuff.
POSIX initially \fIdid\fP make it a size_t, and I (and hopefully others, but
-obviously not too many) complained to them very loudly indeed. Making
-it a size_t is completely broken, exactly because size_t very seldom is
-the same size as "int" on 64-bit architectures, for example. And it
+obviously not too many) complained to them very loudly indeed.
+Making it a size_t is completely broken, exactly because size_t very
+seldom is the same size as "int" on 64-bit architectures, for example.
+And it
\fIhas\fP to be the same size as "int" because that's what the BSD socket
-interface is.
-Anyway, the POSIX people eventually got a clue, and created "socklen_t".
+interface is.
+Anyway, the POSIX people eventually got a clue, and created "socklen_t".
They shouldn't have touched it in the first place, but once they did
they felt it had to have a named type for some unfathomable reason
(probably somebody didn't like losing face over having done the original
projects / thirdparty / man-pages.git / blobdiff