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124 .\" ========================================================================
126 .IX Title "BIO_s_accept 3"
127 .TH BIO_s_accept 3 "2014-04-07" "1.0.1g" "OpenSSL"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
129 .\" way too many mistakes in technical documents.
133 BIO_s_accept, BIO_set_accept_port, BIO_get_accept_port,
134 BIO_set_nbio_accept, BIO_set_accept_bios, BIO_set_bind_mode,
135 BIO_get_bind_mode, BIO_do_accept \- accept BIO
137 .IX Header "SYNOPSIS"
139 \& #include <openssl/bio.h>
141 \& BIO_METHOD *BIO_s_accept(void);
143 \& long BIO_set_accept_port(BIO *b, char *name);
144 \& char *BIO_get_accept_port(BIO *b);
146 \& BIO *BIO_new_accept(char *host_port);
148 \& long BIO_set_nbio_accept(BIO *b, int n);
149 \& long BIO_set_accept_bios(BIO *b, char *bio);
151 \& long BIO_set_bind_mode(BIO *b, long mode);
152 \& long BIO_get_bind_mode(BIO *b, long dummy);
154 \& #define BIO_BIND_NORMAL 0
155 \& #define BIO_BIND_REUSEADDR_IF_UNUSED 1
156 \& #define BIO_BIND_REUSEADDR 2
158 \& int BIO_do_accept(BIO *b);
161 .IX Header "DESCRIPTION"
162 \&\fIBIO_s_accept()\fR returns the accept \s-1BIO\s0 method. This is a wrapper
163 round the platform's \s-1TCP/IP\s0 socket accept routines.
165 Using accept BIOs, \s-1TCP/IP\s0 connections can be accepted and data
166 transferred using only \s-1BIO\s0 routines. In this way any platform
167 specific operations are hidden by the \s-1BIO\s0 abstraction.
169 Read and write operations on an accept \s-1BIO\s0 will perform I/O
170 on the underlying connection. If no connection is established
171 and the port (see below) is set up properly then the \s-1BIO\s0
172 waits for an incoming connection.
174 Accept BIOs support \fIBIO_puts()\fR but not \fIBIO_gets()\fR.
176 If the close flag is set on an accept \s-1BIO\s0 then any active
177 connection on that chain is shutdown and the socket closed when
178 the \s-1BIO\s0 is freed.
180 Calling \fIBIO_reset()\fR on a accept \s-1BIO\s0 will close any active
181 connection and reset the \s-1BIO\s0 into a state where it awaits another
184 \&\fIBIO_get_fd()\fR and \fIBIO_set_fd()\fR can be called to retrieve or set
185 the accept socket. See \fIBIO_s_fd\fR\|(3)
187 \&\fIBIO_set_accept_port()\fR uses the string \fBname\fR to set the accept
188 port. The port is represented as a string of the form \*(L"host:port\*(R",
189 where \*(L"host\*(R" is the interface to use and \*(L"port\*(R" is the port.
190 Either or both values can be \*(L"*\*(R" which is interpreted as meaning
191 any interface or port respectively. \*(L"port\*(R" has the same syntax
192 as the port specified in \fIBIO_set_conn_port()\fR for connect BIOs,
193 that is it can be a numerical port string or a string to lookup
194 using \fIgetservbyname()\fR and a string table.
196 \&\fIBIO_new_accept()\fR combines \fIBIO_new()\fR and \fIBIO_set_accept_port()\fR into
197 a single call: that is it creates a new accept \s-1BIO\s0 with port
200 \&\fIBIO_set_nbio_accept()\fR sets the accept socket to blocking mode
201 (the default) if \fBn\fR is 0 or non blocking mode if \fBn\fR is 1.
203 \&\fIBIO_set_accept_bios()\fR can be used to set a chain of BIOs which
204 will be duplicated and prepended to the chain when an incoming
205 connection is received. This is useful if, for example, a
206 buffering or \s-1SSL\s0 \s-1BIO\s0 is required for each connection. The
207 chain of BIOs must not be freed after this call, they will
208 be automatically freed when the accept \s-1BIO\s0 is freed.
210 \&\fIBIO_set_bind_mode()\fR and \fIBIO_get_bind_mode()\fR set and retrieve
211 the current bind mode. If \s-1BIO_BIND_NORMAL\s0 (the default) is set
212 then another socket cannot be bound to the same port. If
213 \&\s-1BIO_BIND_REUSEADDR\s0 is set then other sockets can bind to the
214 same port. If \s-1BIO_BIND_REUSEADDR_IF_UNUSED\s0 is set then and
215 attempt is first made to use \s-1BIO_BIN_NORMAL\s0, if this fails
216 and the port is not in use then a second attempt is made
217 using \s-1BIO_BIND_REUSEADDR\s0.
219 \&\fIBIO_do_accept()\fR serves two functions. When it is first
220 called, after the accept \s-1BIO\s0 has been setup, it will attempt
221 to create the accept socket and bind an address to it. Second
222 and subsequent calls to \fIBIO_do_accept()\fR will await an incoming
223 connection, or request a retry in non blocking mode.
226 When an accept \s-1BIO\s0 is at the end of a chain it will await an
227 incoming connection before processing I/O calls. When an accept
228 \&\s-1BIO\s0 is not at then end of a chain it passes I/O calls to the next
229 \&\s-1BIO\s0 in the chain.
231 When a connection is established a new socket \s-1BIO\s0 is created for
232 the connection and appended to the chain. That is the chain is now
233 accept\->socket. This effectively means that attempting I/O on
234 an initial accept socket will await an incoming connection then
237 If any additional BIOs have been set using \fIBIO_set_accept_bios()\fR
238 then they are placed between the socket and the accept \s-1BIO\s0,
239 that is the chain will be accept\->otherbios\->socket.
241 If a server wishes to process multiple connections (as is normally
242 the case) then the accept \s-1BIO\s0 must be made available for further
243 incoming connections. This can be done by waiting for a connection and
247 \& connection = BIO_pop(accept);
250 After this call \fBconnection\fR will contain a \s-1BIO\s0 for the recently
251 established connection and \fBaccept\fR will now be a single \s-1BIO\s0
252 again which can be used to await further incoming connections.
253 If no further connections will be accepted the \fBaccept\fR can
254 be freed using \fIBIO_free()\fR.
256 If only a single connection will be processed it is possible to
257 perform I/O using the accept \s-1BIO\s0 itself. This is often undesirable
258 however because the accept \s-1BIO\s0 will still accept additional incoming
259 connections. This can be resolved by using \fIBIO_pop()\fR (see above)
260 and freeing up the accept \s-1BIO\s0 after the initial connection.
262 If the underlying accept socket is non-blocking and \fIBIO_do_accept()\fR is
263 called to await an incoming connection it is possible for
264 \&\fIBIO_should_io_special()\fR with the reason \s-1BIO_RR_ACCEPT\s0. If this happens
265 then it is an indication that an accept attempt would block: the application
266 should take appropriate action to wait until the underlying socket has
267 accepted a connection and retry the call.
269 \&\fIBIO_set_accept_port()\fR, \fIBIO_get_accept_port()\fR, \fIBIO_set_nbio_accept()\fR,
270 \&\fIBIO_set_accept_bios()\fR, \fIBIO_set_bind_mode()\fR, \fIBIO_get_bind_mode()\fR and
271 \&\fIBIO_do_accept()\fR are macros.
273 .IX Header "RETURN VALUES"
277 This example accepts two connections on port 4444, sends messages
278 down each and finally closes both down.
281 \& BIO *abio, *cbio, *cbio2;
282 \& ERR_load_crypto_strings();
283 \& abio = BIO_new_accept("4444");
285 \& /* First call to BIO_accept() sets up accept BIO */
286 \& if(BIO_do_accept(abio) <= 0) {
287 \& fprintf(stderr, "Error setting up accept\en");
288 \& ERR_print_errors_fp(stderr);
292 \& /* Wait for incoming connection */
293 \& if(BIO_do_accept(abio) <= 0) {
294 \& fprintf(stderr, "Error accepting connection\en");
295 \& ERR_print_errors_fp(stderr);
298 \& fprintf(stderr, "Connection 1 established\en");
299 \& /* Retrieve BIO for connection */
300 \& cbio = BIO_pop(abio);
301 \& BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\en");
302 \& fprintf(stderr, "Sent out data on connection 1\en");
303 \& /* Wait for another connection */
304 \& if(BIO_do_accept(abio) <= 0) {
305 \& fprintf(stderr, "Error accepting connection\en");
306 \& ERR_print_errors_fp(stderr);
309 \& fprintf(stderr, "Connection 2 established\en");
310 \& /* Close accept BIO to refuse further connections */
311 \& cbio2 = BIO_pop(abio);
313 \& BIO_puts(cbio2, "Connection 2: Sending out Data on second\en");
314 \& fprintf(stderr, "Sent out data on connection 2\en");
316 \& BIO_puts(cbio, "Connection 1: Second connection established\en");
317 \& /* Close the two established connections */
322 .IX Header "SEE ALSO"