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1.1 root 1: .\" Copyright (c) 1983, 1990 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted
5: .\" provided that: (1) source distributions retain this entire copyright
6: .\" notice and comment, and (2) distributions including binaries display
7: .\" the following acknowledgement: ``This product includes software
8: .\" developed by the University of California, Berkeley and its contributors''
9: .\" in the documentation or other materials provided with the distribution
10: .\" and in all advertising materials mentioning features or use of this
11: .\" software. Neither the name of the University nor the names of its
12: .\" contributors may be used to endorse or promote products derived
13: .\" from this software without specific prior written permission.
14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
15: .\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
16: .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17: .\"
18: .\" @(#)accept.2 6.5 (Berkeley) 5/30/90
19: .\"
20: .TH ACCEPT 2 "May 30, 1990"
21: .UC 5
22: .SH NAME
23: accept \- accept a connection on a socket
24: .SH SYNOPSIS
25: .ft B
26: .nf
27: #include <sys/types.h>
28: #include <sys/socket.h>
29: .PP
30: .ft B
31: ns = accept(s, addr, addrlen)
32: int ns, s;
33: struct sockaddr *addr;
34: int *addrlen;
35: .fi
36: .SH DESCRIPTION
37: The argument
38: .I s
39: is a socket that has been created with
40: .IR socket (2),
41: bound to an address with
42: .IR bind (2),
43: and is listening for connections after a
44: .IR listen (2).
45: .I Accept
46: extracts the first connection request
47: on the queue of pending connections, creates
48: a new socket with the same properties of
49: .I s
50: and allocates a new file descriptor,
51: .IR ns ,
52: for the socket. If no pending connections are
53: present on the queue, and the socket is not marked
54: as non-blocking,
55: .I accept
56: blocks the caller until a connection is present.
57: If the socket is marked non-blocking and no pending
58: connections are present on the queue,
59: .I accept
60: returns an error as described below.
61: The accepted socket,
62: .IR ns ,
63: may not be used
64: to accept more connections. The original socket
65: .I s
66: remains open.
67: .PP
68: The argument
69: .I addr
70: is a result parameter that is filled in with
71: the address of the connecting entity,
72: as known to the communications layer.
73: The exact format of the
74: .I addr
75: parameter is determined by the domain in which the communication
76: is occurring.
77: The
78: .I addrlen
79: is a value-result parameter; it should initially contain the
80: amount of space pointed to by
81: .IR addr ;
82: on return it will contain the actual length (in bytes) of the
83: address returned.
84: This call
85: is used with connection-based socket types, currently with SOCK_STREAM.
86: .PP
87: It is possible to
88: .IR select (2)
89: a socket for the purposes of doing an
90: .I accept
91: by selecting it for read.
92: .PP
93: For certain protocols which require an explicit confirmation,
94: such as ISO or DATAKIT,
95: one should think of accept as merely dequeueing the next connection
96: request, and not in of itself implying confirmation.
97: Confirmation can be implied by a normal read or write on the new
98: file desciptor, and rejection can be implied by closing the
99: new socket.
100: .PP
101: One can obtain user connection request data without confirming
102: the connection by issuing a
103: recvmsg call with an msg_iovlen of 0 and a non-zero
104: msg_controllen, or by issuing a
105: .IR getsockopt (2)
106: request.
107: Similarly, one can provide user connection rejection information
108: by issuing a sendmsg call with providing only the control information,
109: or by calling
110: .IR setsockopt (2).
111: .SH "RETURN VALUE
112: The call returns \-1 on error. If it succeeds, it returns a non-negative
113: integer that is a descriptor for the accepted socket.
114: .SH ERRORS
115: The \fIaccept\fP will fail if:
116: .TP 20
117: [EBADF]
118: The descriptor is invalid.
119: .TP 20
120: [ENOTSOCK]
121: The descriptor references a file, not a socket.
122: .TP 20
123: [EOPNOTSUPP]
124: The referenced socket is not of type SOCK_STREAM.
125: .TP 20
126: [EFAULT]
127: The \fIaddr\fP parameter is not in a writable part of the
128: user address space.
129: .TP 20
130: [EWOULDBLOCK]
131: The socket is marked non-blocking and no connections
132: are present to be accepted.
133: .SH SEE ALSO
134: bind(2), connect(2), listen(2), select(2), socket(2)
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