1BIO_S_ACCEPT(3) OpenSSL BIO_S_ACCEPT(3)
2
6 BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port,
7 BIO_get_accept_name, BIO_get_accept_port, BIO_new_accept,
8 BIO_set_nbio_accept, BIO_set_accept_bios, BIO_get_peer_name,
9 BIO_get_peer_port, BIO_get_accept_ip_family, BIO_set_accept_ip_family,
10 BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept - accept BIO
11
13 #include <openssl/bio.h>
14 const BIO_METHOD *BIO_s_accept(void);
16 long BIO_set_accept_name(BIO *b, char *name);
18 char *BIO_get_accept_name(BIO *b);
19 long BIO_set_accept_port(BIO *b, char *port);
21 char *BIO_get_accept_port(BIO *b);
22 BIO *BIO_new_accept(char *host_port);
24 long BIO_set_nbio_accept(BIO *b, int n);
26 long BIO_set_accept_bios(BIO *b, char *bio);
27 char *BIO_get_peer_name(BIO *b);
29 char *BIO_get_peer_port(BIO *b);
30 long BIO_get_accept_ip_family(BIO *b);
31 long BIO_set_accept_ip_family(BIO *b, long family);
32 long BIO_set_bind_mode(BIO *b, long mode);
34 long BIO_get_bind_mode(BIO *b);
35 int BIO_do_accept(BIO *b);
37
39 BIO_s_accept() returns the accept BIO method. This is a wrapper round
40 the platform's TCP/IP socket accept routines.
41 Using accept BIOs, TCP/IP connections can be accepted and data
43 transferred using only BIO routines. In this way any platform specific
44 operations are hidden by the BIO abstraction.
45 Read and write operations on an accept BIO will perform I/O on the
47 underlying connection. If no connection is established and the port
48 (see below) is set up properly then the BIO waits for an incoming
49 connection.
50 Accept BIOs support BIO_puts() but not BIO_gets().
52 If the close flag is set on an accept BIO then any active connection on
54 that chain is shutdown and the socket closed when the BIO is freed.
55 Calling BIO_reset() on an accept BIO will close any active connection
57 and reset the BIO into a state where it awaits another incoming
58 connection.
59 BIO_get_fd() and BIO_set_fd() can be called to retrieve or set the
61 accept socket. See BIO_s_fd(3)
62 BIO_set_accept_name() uses the string name to set the accept name. The
64 name is represented as a string of the form "host:port", where "host"
65 is the interface to use and "port" is the port. The host can be "*" or
66 empty which is interpreted as meaning any interface. If the host is an
67 IPv6 address, it has to be enclosed in brackets, for example
68 "[::1]:https". "port" has the same syntax as the port specified in
69 BIO_set_conn_port() for connect BIOs, that is it can be a numerical
70 port string or a string to lookup using getservbyname() and a string
71 table.
72 BIO_set_accept_port() uses the string port to set the accept port.
74 "port" has the same syntax as the port specified in BIO_set_conn_port()
75 for connect BIOs, that is it can be a numerical port string or a string
76 to lookup using getservbyname() and a string table.
77 BIO_new_accept() combines BIO_new() and BIO_set_accept_name() into a
79 single call: that is it creates a new accept BIO with port host_port.
80 BIO_set_nbio_accept() sets the accept socket to blocking mode (the
82 default) if n is 0 or non blocking mode if n is 1.
83 BIO_set_accept_bios() can be used to set a chain of BIOs which will be
85 duplicated and prepended to the chain when an incoming connection is
86 received. This is useful if, for example, a buffering or SSL BIO is
87 required for each connection. The chain of BIOs must not be freed after
88 this call, they will be automatically freed when the accept BIO is
89 freed.
90 BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve the
92 current bind mode. If BIO_BIND_NORMAL (the default) is set then another
93 socket cannot be bound to the same port. If BIO_BIND_REUSEADDR is set
94 then other sockets can bind to the same port. If
95 BIO_BIND_REUSEADDR_IF_UNUSED is set then and attempt is first made to
96 use BIO_BIN_NORMAL, if this fails and the port is not in use then a
97 second attempt is made using BIO_BIND_REUSEADDR.
98 BIO_do_accept() serves two functions. When it is first called, after
100 the accept BIO has been setup, it will attempt to create the accept
101 socket and bind an address to it. Second and subsequent calls to
102 BIO_do_accept() will await an incoming connection, or request a retry
103 in non blocking mode.
104
106 When an accept BIO is at the end of a chain it will await an incoming
107 connection before processing I/O calls. When an accept BIO is not at
108 then end of a chain it passes I/O calls to the next BIO in the chain.
109 When a connection is established a new socket BIO is created for the
111 connection and appended to the chain. That is the chain is now
112 accept->socket. This effectively means that attempting I/O on an
113 initial accept socket will await an incoming connection then perform
114 I/O on it.
115 If any additional BIOs have been set using BIO_set_accept_bios() then
117 they are placed between the socket and the accept BIO, that is the
118 chain will be accept->otherbios->socket.
119 If a server wishes to process multiple connections (as is normally the
121 case) then the accept BIO must be made available for further incoming
122 connections. This can be done by waiting for a connection and then
123 calling:
124 connection = BIO_pop(accept);
126 After this call connection will contain a BIO for the recently
128 established connection and accept will now be a single BIO again which
129 can be used to await further incoming connections. If no further
130 connections will be accepted the accept can be freed using BIO_free().
131 If only a single connection will be processed it is possible to perform
133 I/O using the accept BIO itself. This is often undesirable however
134 because the accept BIO will still accept additional incoming
135 connections. This can be resolved by using BIO_pop() (see above) and
136 freeing up the accept BIO after the initial connection.
137 If the underlying accept socket is nonblocking and BIO_do_accept() is
139 called to await an incoming connection it is possible for
140 BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens
141 then it is an indication that an accept attempt would block: the
142 application should take appropriate action to wait until the underlying
143 socket has accepted a connection and retry the call.
144 BIO_set_accept_name(), BIO_get_accept_name(), BIO_set_accept_port(),
146 BIO_get_accept_port(), BIO_set_nbio_accept(), BIO_set_accept_bios(),
147 BIO_get_peer_name(), BIO_get_peer_port(), BIO_get_accept_ip_family(),
148 BIO_set_accept_ip_family(), BIO_set_bind_mode(), BIO_get_bind_mode()
149 and BIO_do_accept() are macros.
150
152 BIO_do_accept(), BIO_set_accept_name(), BIO_set_accept_port(),
153 BIO_set_nbio_accept(), BIO_set_accept_bios(),
154 BIO_set_accept_ip_family(), and BIO_set_bind_mode() return 1 for
155 success and 0 or -1 for failure.
156 BIO_get_accept_name() returns the accept name or NULL on error.
158 BIO_get_peer_name() returns the peer name or NULL on error.
159 BIO_get_accept_port() returns the accept port as a string or NULL on
161 error. BIO_get_peer_port() returns the peer port as a string or NULL
162 on error. BIO_get_accept_ip_family() returns the IP family or -1 on
163 error.
164 BIO_get_bind_mode() returns the set of BIO_BIND flags, or -1 on
166 failure.
167 BIO_new_accept() returns a BIO or NULL on error.
169
171 This example accepts two connections on port 4444, sends messages down
172 each and finally closes both down.
173 BIO *abio, *cbio, *cbio2;
175 /* First call to BIO_accept() sets up accept BIO */
177 abio = BIO_new_accept("4444");
178 if (BIO_do_accept(abio) <= 0) {
179 fprintf(stderr, "Error setting up accept\n");
180 ERR_print_errors_fp(stderr);
181 exit(1);
182 }
183 /* Wait for incoming connection */
185 if (BIO_do_accept(abio) <= 0) {
186 fprintf(stderr, "Error accepting connection\n");
187 ERR_print_errors_fp(stderr);
188 exit(1);
189 }
190 fprintf(stderr, "Connection 1 established\n");
191 /* Retrieve BIO for connection */
193 cbio = BIO_pop(abio);
194 BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
195 fprintf(stderr, "Sent out data on connection 1\n");
196 /* Wait for another connection */
198 if (BIO_do_accept(abio) <= 0) {
199 fprintf(stderr, "Error accepting connection\n");
200 ERR_print_errors_fp(stderr);
201 exit(1);
202 }
203 fprintf(stderr, "Connection 2 established\n");
204 /* Close accept BIO to refuse further connections */
206 cbio2 = BIO_pop(abio);
207 BIO_free(abio);
208 BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
209 fprintf(stderr, "Sent out data on connection 2\n");
210 BIO_puts(cbio, "Connection 1: Second connection established\n");
212 /* Close the two established connections */
214 BIO_free(cbio);
215 BIO_free(cbio2);
216
218 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
219 Licensed under the OpenSSL license (the "License"). You may not use
221 this file except in compliance with the License. You can obtain a copy
222 in the file LICENSE in the source distribution or at
223 <https://www.openssl.org/source/license.html>.
2241.1.1l 2021-09-15 BIO_S_ACCEPT(3)