| 1 |
786 |
skrzyp |
<html>
|
| 2 |
|
|
<body>
|
| 3 |
|
|
<pre>
|
| 4 |
|
|
NAME
|
| 5 |
|
|
accept - accept a connection on a socket
|
| 6 |
|
|
|
| 7 |
|
|
SYNOPSIS
|
| 8 |
|
|
#include <network.h>
|
| 9 |
|
|
|
| 10 |
|
|
int accept(int s, struct sockaddr *addr, int *addrlen);
|
| 11 |
|
|
|
| 12 |
|
|
DESCRIPTION
|
| 13 |
|
|
The argument s is a socket that has been created with
|
| 14 |
|
|
socket(2), bound to an address with bind(2), and is lis-
|
| 15 |
|
|
tening for connections after a listen(2). The accept
|
| 16 |
|
|
function extracts the first connection request on the
|
| 17 |
|
|
queue of pending connections, creates a new socket with
|
| 18 |
|
|
the same properties of s, and allocates a new file
|
| 19 |
|
|
descriptor for the socket. If no pending connections are
|
| 20 |
|
|
present on the queue, and the socket is not marked as non-
|
| 21 |
|
|
blocking, accept blocks the caller until a connection is
|
| 22 |
|
|
present. If the socket is marked non-blocking and no
|
| 23 |
|
|
pending connections are present on the queue, accept
|
| 24 |
|
|
returns an error as described below. The socket returned
|
| 25 |
|
|
by accept may not be used to accept more connections. The
|
| 26 |
|
|
original socket s remains open.
|
| 27 |
|
|
|
| 28 |
|
|
The argument addr is a result parameter that is filled in
|
| 29 |
|
|
with the address of the connecting entity, as known to the
|
| 30 |
|
|
communications layer. The exact format of the addr param-
|
| 31 |
|
|
eter is determined by the domain in which the communica-
|
| 32 |
|
|
tion is occurring. addrlen is a value-result parameter:
|
| 33 |
|
|
it should initially contain the amount of space pointed to
|
| 34 |
|
|
by addr; on return it will contain the actual length (in
|
| 35 |
|
|
bytes) of the address returned. This call is used with
|
| 36 |
|
|
connection-based socket types, currently with SOCK_STREAM.
|
| 37 |
|
|
|
| 38 |
|
|
It is possible to select(2) a socket for the purposes of
|
| 39 |
|
|
doing an accept by selecting it for read.
|
| 40 |
|
|
|
| 41 |
|
|
For certain protocols which require an explicit confirma-
|
| 42 |
|
|
tion, such as DECNet, accept can be thought of as merely
|
| 43 |
|
|
dequeuing the next connection request and not implying
|
| 44 |
|
|
confirmation. Confirmation can be implied by a normal
|
| 45 |
|
|
read or write on the new file descriptor, and rejection
|
| 46 |
|
|
can be implied by closing the new socket. Currently only
|
| 47 |
|
|
DECNet has these semantics on Linux.
|
| 48 |
|
|
|
| 49 |
|
|
NOTES
|
| 50 |
|
|
If you want accept to never block the listening socket
|
| 51 |
|
|
needs to have the non blocking flag set. Assuming that
|
| 52 |
|
|
there is always a connection waiting after select returned
|
| 53 |
|
|
true is not reliable, because the connection might be
|
| 54 |
|
|
removed by an asynchronous network error between the
|
| 55 |
|
|
select/poll returning and the accept call. The application
|
| 56 |
|
|
would hang then if the listen socket is not non blocking.
|
| 57 |
|
|
|
| 58 |
|
|
RETURN VALUES
|
| 59 |
|
|
The call returns -1 on error. If it succeeds, it returns
|
| 60 |
|
|
a non-negative integer that is a descriptor for the
|
| 61 |
|
|
accepted socket.
|
| 62 |
|
|
|
| 63 |
|
|
ERRORS
|
| 64 |
|
|
EBADF The descriptor is invalid.
|
| 65 |
|
|
|
| 66 |
|
|
ENOTSOCK
|
| 67 |
|
|
The descriptor references a file, not a socket.
|
| 68 |
|
|
|
| 69 |
|
|
EOPNOTSUPP
|
| 70 |
|
|
The referenced socket is not of type SOCK_STREAM.
|
| 71 |
|
|
|
| 72 |
|
|
EAGAIN The socket is marked non-blocking and no connec-
|
| 73 |
|
|
tions are present to be accepted.
|
| 74 |
|
|
|
| 75 |
|
|
ENOBUFS, ENOMEM
|
| 76 |
|
|
Not enough free memory.
|
| 77 |
|
|
|
| 78 |
|
|
|
| 79 |
|
|
</pre>
|
| 80 |
|
|
</body>
|
| 81 |
|
|
</html>
|
