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133 .\" ========================================================================
135 .IX Title "BIO_S_ACCEPT 3"
136 .TH BIO_S_ACCEPT 3 "2020-12-08" "1.1.1i" "OpenSSL"
137 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
138 .\" way too many mistakes in technical documents.
142 BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port, BIO_get_accept_name, BIO_get_accept_port, BIO_new_accept, BIO_set_nbio_accept, BIO_set_accept_bios, BIO_get_peer_name, BIO_get_peer_port, BIO_get_accept_ip_family, BIO_set_accept_ip_family, BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept \- accept BIO
144 .IX Header "SYNOPSIS"
146 \& #include <openssl/bio.h>
148 \& const BIO_METHOD *BIO_s_accept(void);
150 \& long BIO_set_accept_name(BIO *b, char *name);
151 \& char *BIO_get_accept_name(BIO *b);
153 \& long BIO_set_accept_port(BIO *b, char *port);
154 \& char *BIO_get_accept_port(BIO *b);
156 \& BIO *BIO_new_accept(char *host_port);
158 \& long BIO_set_nbio_accept(BIO *b, int n);
159 \& long BIO_set_accept_bios(BIO *b, char *bio);
161 \& char *BIO_get_peer_name(BIO *b);
162 \& char *BIO_get_peer_port(BIO *b);
163 \& long BIO_get_accept_ip_family(BIO *b);
164 \& long BIO_set_accept_ip_family(BIO *b, long family);
166 \& long BIO_set_bind_mode(BIO *b, long mode);
167 \& long BIO_get_bind_mode(BIO *b);
169 \& int BIO_do_accept(BIO *b);
172 .IX Header "DESCRIPTION"
173 \&\fBBIO_s_accept()\fR returns the accept \s-1BIO\s0 method. This is a wrapper
174 round the platform's \s-1TCP/IP\s0 socket accept routines.
176 Using accept BIOs, \s-1TCP/IP\s0 connections can be accepted and data
177 transferred using only \s-1BIO\s0 routines. In this way any platform
178 specific operations are hidden by the \s-1BIO\s0 abstraction.
180 Read and write operations on an accept \s-1BIO\s0 will perform I/O
181 on the underlying connection. If no connection is established
182 and the port (see below) is set up properly then the \s-1BIO\s0
183 waits for an incoming connection.
185 Accept BIOs support \fBBIO_puts()\fR but not \fBBIO_gets()\fR.
187 If the close flag is set on an accept \s-1BIO\s0 then any active
188 connection on that chain is shutdown and the socket closed when
189 the \s-1BIO\s0 is freed.
191 Calling \fBBIO_reset()\fR on an accept \s-1BIO\s0 will close any active
192 connection and reset the \s-1BIO\s0 into a state where it awaits another
195 \&\fBBIO_get_fd()\fR and \fBBIO_set_fd()\fR can be called to retrieve or set
196 the accept socket. See \fBBIO_s_fd\fR\|(3)
198 \&\fBBIO_set_accept_name()\fR uses the string \fBname\fR to set the accept
199 name. The name is represented as a string of the form \*(L"host:port\*(R",
200 where \*(L"host\*(R" is the interface to use and \*(L"port\*(R" is the port.
201 The host can be \*(L"*\*(R" or empty which is interpreted as meaning
202 any interface. If the host is an IPv6 address, it has to be
203 enclosed in brackets, for example \*(L"[::1]:https\*(R". \*(L"port\*(R" has the
204 same syntax as the port specified in \fBBIO_set_conn_port()\fR for
205 connect BIOs, that is it can be a numerical port string or a
206 string to lookup using \fBgetservbyname()\fR and a string table.
208 \&\fBBIO_set_accept_port()\fR uses the string \fBport\fR to set the accept
209 port. \*(L"port\*(R" has the same syntax as the port specified in
210 \&\fBBIO_set_conn_port()\fR for connect BIOs, that is it can be a numerical
211 port string or a string to lookup using \fBgetservbyname()\fR and a string
214 \&\fBBIO_new_accept()\fR combines \fBBIO_new()\fR and \fBBIO_set_accept_name()\fR into
215 a single call: that is it creates a new accept \s-1BIO\s0 with port
218 \&\fBBIO_set_nbio_accept()\fR sets the accept socket to blocking mode
219 (the default) if \fBn\fR is 0 or non blocking mode if \fBn\fR is 1.
221 \&\fBBIO_set_accept_bios()\fR can be used to set a chain of BIOs which
222 will be duplicated and prepended to the chain when an incoming
223 connection is received. This is useful if, for example, a
224 buffering or \s-1SSL BIO\s0 is required for each connection. The
225 chain of BIOs must not be freed after this call, they will
226 be automatically freed when the accept \s-1BIO\s0 is freed.
228 \&\fBBIO_set_bind_mode()\fR and \fBBIO_get_bind_mode()\fR set and retrieve
229 the current bind mode. If \fB\s-1BIO_BIND_NORMAL\s0\fR (the default) is set
230 then another socket cannot be bound to the same port. If
231 \&\fB\s-1BIO_BIND_REUSEADDR\s0\fR is set then other sockets can bind to the
232 same port. If \fB\s-1BIO_BIND_REUSEADDR_IF_UNUSED\s0\fR is set then and
233 attempt is first made to use \s-1BIO_BIN_NORMAL,\s0 if this fails
234 and the port is not in use then a second attempt is made
235 using \fB\s-1BIO_BIND_REUSEADDR\s0\fR.
237 \&\fBBIO_do_accept()\fR serves two functions. When it is first
238 called, after the accept \s-1BIO\s0 has been setup, it will attempt
239 to create the accept socket and bind an address to it. Second
240 and subsequent calls to \fBBIO_do_accept()\fR will await an incoming
241 connection, or request a retry in non blocking mode.
244 When an accept \s-1BIO\s0 is at the end of a chain it will await an
245 incoming connection before processing I/O calls. When an accept
246 \&\s-1BIO\s0 is not at then end of a chain it passes I/O calls to the next
247 \&\s-1BIO\s0 in the chain.
249 When a connection is established a new socket \s-1BIO\s0 is created for
250 the connection and appended to the chain. That is the chain is now
251 accept\->socket. This effectively means that attempting I/O on
252 an initial accept socket will await an incoming connection then
255 If any additional BIOs have been set using \fBBIO_set_accept_bios()\fR
256 then they are placed between the socket and the accept \s-1BIO,\s0
257 that is the chain will be accept\->otherbios\->socket.
259 If a server wishes to process multiple connections (as is normally
260 the case) then the accept \s-1BIO\s0 must be made available for further
261 incoming connections. This can be done by waiting for a connection and
265 \& connection = BIO_pop(accept);
268 After this call \fBconnection\fR will contain a \s-1BIO\s0 for the recently
269 established connection and \fBaccept\fR will now be a single \s-1BIO\s0
270 again which can be used to await further incoming connections.
271 If no further connections will be accepted the \fBaccept\fR can
272 be freed using \fBBIO_free()\fR.
274 If only a single connection will be processed it is possible to
275 perform I/O using the accept \s-1BIO\s0 itself. This is often undesirable
276 however because the accept \s-1BIO\s0 will still accept additional incoming
277 connections. This can be resolved by using \fBBIO_pop()\fR (see above)
278 and freeing up the accept \s-1BIO\s0 after the initial connection.
280 If the underlying accept socket is nonblocking and \fBBIO_do_accept()\fR is
281 called to await an incoming connection it is possible for
282 \&\fBBIO_should_io_special()\fR with the reason \s-1BIO_RR_ACCEPT.\s0 If this happens
283 then it is an indication that an accept attempt would block: the application
284 should take appropriate action to wait until the underlying socket has
285 accepted a connection and retry the call.
287 \&\fBBIO_set_accept_name()\fR, \fBBIO_get_accept_name()\fR, \fBBIO_set_accept_port()\fR,
288 \&\fBBIO_get_accept_port()\fR, \fBBIO_set_nbio_accept()\fR, \fBBIO_set_accept_bios()\fR,
289 \&\fBBIO_get_peer_name()\fR, \fBBIO_get_peer_port()\fR,
290 \&\fBBIO_get_accept_ip_family()\fR, \fBBIO_set_accept_ip_family()\fR,
291 \&\fBBIO_set_bind_mode()\fR, \fBBIO_get_bind_mode()\fR and \fBBIO_do_accept()\fR are macros.
293 .IX Header "RETURN VALUES"
294 \&\fBBIO_do_accept()\fR,
295 \&\fBBIO_set_accept_name()\fR, \fBBIO_set_accept_port()\fR, \fBBIO_set_nbio_accept()\fR,
296 \&\fBBIO_set_accept_bios()\fR, \fBBIO_set_accept_ip_family()\fR, and \fBBIO_set_bind_mode()\fR
297 return 1 for success and 0 or \-1 for failure.
299 \&\fBBIO_get_accept_name()\fR returns the accept name or \s-1NULL\s0 on error.
300 \&\fBBIO_get_peer_name()\fR returns the peer name or \s-1NULL\s0 on error.
302 \&\fBBIO_get_accept_port()\fR returns the accept port as a string or \s-1NULL\s0 on error.
303 \&\fBBIO_get_peer_port()\fR returns the peer port as a string or \s-1NULL\s0 on error.
304 \&\fBBIO_get_accept_ip_family()\fR returns the \s-1IP\s0 family or \-1 on error.
306 \&\fBBIO_get_bind_mode()\fR returns the set of \fB\s-1BIO_BIND\s0\fR flags, or \-1 on failure.
308 \&\fBBIO_new_accept()\fR returns a \s-1BIO\s0 or \s-1NULL\s0 on error.
310 .IX Header "EXAMPLES"
311 This example accepts two connections on port 4444, sends messages
312 down each and finally closes both down.
315 \& BIO *abio, *cbio, *cbio2;
317 \& /* First call to BIO_accept() sets up accept BIO */
318 \& abio = BIO_new_accept("4444");
319 \& if (BIO_do_accept(abio) <= 0) {
320 \& fprintf(stderr, "Error setting up accept\en");
321 \& ERR_print_errors_fp(stderr);
325 \& /* Wait for incoming connection */
326 \& if (BIO_do_accept(abio) <= 0) {
327 \& fprintf(stderr, "Error accepting connection\en");
328 \& ERR_print_errors_fp(stderr);
331 \& fprintf(stderr, "Connection 1 established\en");
333 \& /* Retrieve BIO for connection */
334 \& cbio = BIO_pop(abio);
335 \& BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\en");
336 \& fprintf(stderr, "Sent out data on connection 1\en");
338 \& /* Wait for another connection */
339 \& if (BIO_do_accept(abio) <= 0) {
340 \& fprintf(stderr, "Error accepting connection\en");
341 \& ERR_print_errors_fp(stderr);
344 \& fprintf(stderr, "Connection 2 established\en");
346 \& /* Close accept BIO to refuse further connections */
347 \& cbio2 = BIO_pop(abio);
349 \& BIO_puts(cbio2, "Connection 2: Sending out Data on second\en");
350 \& fprintf(stderr, "Sent out data on connection 2\en");
352 \& BIO_puts(cbio, "Connection 1: Second connection established\en");
354 \& /* Close the two established connections */
359 .IX Header "COPYRIGHT"
360 Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
362 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
363 this file except in compliance with the License. You can obtain a copy
364 in the file \s-1LICENSE\s0 in the source distribution or at
365 <https://www.openssl.org/source/license.html>.