| 1 | .\" Copyright (c) 1983 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement |
| 3 | .\" specifies the terms and conditions for redistribution. |
| 4 | .\" |
| 5 | .\" @(#)accept.2 6.2 (Berkeley) %G% |
| 6 | .\" |
| 7 | .TH ACCEPT 2 "" |
| 8 | .UC 5 |
| 9 | .SH NAME |
| 10 | accept \- accept a connection on a socket |
| 11 | .SH SYNOPSIS |
| 12 | .ft B |
| 13 | .nf |
| 14 | #include <sys/types.h> |
| 15 | #include <sys/socket.h> |
| 16 | .PP |
| 17 | .ft B |
| 18 | ns = accept(s, addr, addrlen) |
| 19 | int ns, s; |
| 20 | struct sockaddr *addr; |
| 21 | int *addrlen; |
| 22 | .fi |
| 23 | .SH DESCRIPTION |
| 24 | The argument |
| 25 | .I s |
| 26 | is a socket that has been created with |
| 27 | .IR socket (2), |
| 28 | bound to an address with |
| 29 | .IR bind (2), |
| 30 | and is listening for connections after a |
| 31 | .IR listen (2). |
| 32 | .I Accept |
| 33 | extracts the first connection |
| 34 | on the queue of pending connections, creates |
| 35 | a new socket with the same properties of |
| 36 | .I s |
| 37 | and allocates a new file descriptor, |
| 38 | .IR ns , |
| 39 | for the socket. If no pending connections are |
| 40 | present on the queue, and the socket is not marked |
| 41 | as non-blocking, |
| 42 | .I accept |
| 43 | blocks the caller until a connection is present. |
| 44 | If the socket is marked non-blocking and no pending |
| 45 | connections are present on the queue, |
| 46 | .I accept |
| 47 | returns an error as described below. |
| 48 | The accepted socket, |
| 49 | .IR ns , |
| 50 | may not be used |
| 51 | to accept more connections. The original socket |
| 52 | .I s |
| 53 | remains open. |
| 54 | .PP |
| 55 | The argument |
| 56 | .I addr |
| 57 | is a result parameter that is filled in with |
| 58 | the address of the connecting entity, |
| 59 | as known to the communications layer. |
| 60 | The exact format of the |
| 61 | .I addr |
| 62 | parameter is determined by the domain in which the communication |
| 63 | is occurring. |
| 64 | The |
| 65 | .I addrlen |
| 66 | is a value-result parameter; it should initially contain the |
| 67 | amount of space pointed to by |
| 68 | .IR addr ; |
| 69 | on return it will contain the actual length (in bytes) of the |
| 70 | address returned. |
| 71 | This call |
| 72 | is used with connection-based socket types, currently with SOCK_STREAM. |
| 73 | .PP |
| 74 | It is possible to |
| 75 | .IR select (2) |
| 76 | a socket for the purposes of doing an |
| 77 | .I accept |
| 78 | by selecting it for read. |
| 79 | .SH "RETURN VALUE |
| 80 | The call returns \-1 on error. If it succeeds it returns a non-negative |
| 81 | integer that is a descriptor for the accepted socket. |
| 82 | .SH ERRORS |
| 83 | The \fIaccept\fP will fail if: |
| 84 | .TP 20 |
| 85 | [EBADF] |
| 86 | The descriptor is invalid. |
| 87 | .TP 20 |
| 88 | [ENOTSOCK] |
| 89 | The descriptor references a file, not a socket. |
| 90 | .TP 20 |
| 91 | [EOPNOTSUPP] |
| 92 | The referenced socket is not of type SOCK_STREAM. |
| 93 | .TP 20 |
| 94 | [EFAULT] |
| 95 | The \fIaddr\fP parameter is not in a writable part of the |
| 96 | user address space. |
| 97 | .TP 20 |
| 98 | [EWOULDBLOCK] |
| 99 | The socket is marked non-blocking and no connections |
| 100 | are present to be accepted. |
| 101 | .SH SEE ALSO |
| 102 | bind(2), connect(2), listen(2), select(2), socket(2) |