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138.\" ======================================================================
139.\"
140.IX Title "BIO_s_accept 3"
141.TH BIO_s_accept 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144BIO_s_accept, BIO_set_accept_port, BIO_get_accept_port,
145BIO_set_nbio_accept, BIO_set_accept_bios, BIO_set_bind_mode,
146BIO_get_bind_mode, BIO_do_accept \- accept \s-1BIO\s0
147.SH "SYNOPSIS"
148.IX Header "SYNOPSIS"
149.Vb 1
150\& #include <openssl/bio.h>
151.Ve
152.Vb 1
153\& BIO_METHOD *BIO_s_accept(void);
154.Ve
155.Vb 2
156\& long BIO_set_accept_port(BIO *b, char *name);
157\& char *BIO_get_accept_port(BIO *b);
158.Ve
159.Vb 1
160\& BIO *BIO_new_accept(char *host_port);
161.Ve
162.Vb 2
163\& long BIO_set_nbio_accept(BIO *b, int n);
164\& long BIO_set_accept_bios(BIO *b, char *bio);
165.Ve
166.Vb 2
167\& long BIO_set_bind_mode(BIO *b, long mode);
168\& long BIO_get_bind_mode(BIO *b, long dummy);
169.Ve
170.Vb 3
171\& #define BIO_BIND_NORMAL 0
172\& #define BIO_BIND_REUSEADDR_IF_UNUSED 1
173\& #define BIO_BIND_REUSEADDR 2
174.Ve
175.Vb 1
176\& int BIO_do_accept(BIO *b);
177.Ve
178.SH "DESCRIPTION"
179.IX Header "DESCRIPTION"
180\&\fIBIO_s_accept()\fR returns the accept \s-1BIO\s0 method. This is a wrapper
181round the platform's \s-1TCP/IP\s0 socket accept routines.
182.PP
183Using accept BIOs, \s-1TCP/IP\s0 connections can be accepted and data
184transferred using only \s-1BIO\s0 routines. In this way any platform
185specific operations are hidden by the \s-1BIO\s0 abstraction.
186.PP
187Read and write operations on an accept \s-1BIO\s0 will perform I/O
188on the underlying connection. If no connection is established
189and the port (see below) is set up properly then the \s-1BIO\s0
190waits for an incoming connection.
191.PP
192Accept BIOs support \fIBIO_puts()\fR but not \fIBIO_gets()\fR.
193.PP
194If the close flag is set on an accept \s-1BIO\s0 then any active
195connection on that chain is shutdown and the socket closed when
196the \s-1BIO\s0 is freed.
197.PP
198Calling \fIBIO_reset()\fR on a accept \s-1BIO\s0 will close any active
199connection and reset the \s-1BIO\s0 into a state where it awaits another
200incoming connection.
201.PP
202\&\fIBIO_get_fd()\fR and \fIBIO_set_fd()\fR can be called to retrieve or set
203the accept socket. See BIO_s_fd(3)
204.PP
205\&\fIBIO_set_accept_port()\fR uses the string \fBname\fR to set the accept
206port. The port is represented as a string of the form \*(L"host:port\*(R",
207where \*(L"host\*(R" is the interface to use and \*(L"port\*(R" is the port.
208Either or both values can be \*(L"*\*(R" which is interpreted as meaning
209any interface or port respectively. \*(L"port\*(R" has the same syntax
210as the port specified in \fIBIO_set_conn_port()\fR for connect BIOs,
211that is it can be a numerical port string or a string to lookup
212using \fIgetservbyname()\fR and a string table.
213.PP
214\&\fIBIO_new_accept()\fR combines \fIBIO_new()\fR and \fIBIO_set_accept_port()\fR into
215a single call: that is it creates a new accept \s-1BIO\s0 with port
216\&\fBhost_port\fR.
217.PP
218\&\fIBIO_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.
220.PP
221\&\fIBIO_set_accept_bios()\fR can be used to set a chain of BIOs which
222will be duplicated and prepended to the chain when an incoming
223connection is received. This is useful if, for example, a
224buffering or \s-1SSL\s0 \s-1BIO\s0 is required for each connection. The
225chain of BIOs must not be freed after this call, they will
226be automatically freed when the accept \s-1BIO\s0 is freed.
227.PP
228\&\fIBIO_set_bind_mode()\fR and \fIBIO_get_bind_mode()\fR set and retrieve
229the current bind mode. If \s-1BIO_BIND_NORMAL\s0 (the default) is set
230then another socket cannot be bound to the same port. If
231\&\s-1BIO_BIND_REUSEADDR\s0 is set then other sockets can bind to the
232same port. If \s-1BIO_BIND_REUSEADDR_IF_UNUSED\s0 is set then and
233attempt is first made to use \s-1BIO_BIN_NORMAL\s0, if this fails
234and the port is not in use then a second attempt is made
235using \s-1BIO_BIND_REUSEADDR\s0.
236.PP
237\&\fIBIO_do_accept()\fR serves two functions. When it is first
238called, after the accept \s-1BIO\s0 has been setup, it will attempt
239to create the accept socket and bind an address to it. Second
240and subsequent calls to \fIBIO_do_accept()\fR will await an incoming
241connection, or request a retry in non blocking mode.
242.SH "NOTES"
243.IX Header "NOTES"
244When an accept \s-1BIO\s0 is at the end of a chain it will await an
245incoming 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.
248.PP
249When a connection is established a new socket \s-1BIO\s0 is created for
250the connection and appended to the chain. That is the chain is now
251accept->socket. This effectively means that attempting I/O on
252an initial accept socket will await an incoming connection then
253perform I/O on it.
254.PP
255If any additional BIOs have been set using \fIBIO_set_accept_bios()\fR
256then they are placed between the socket and the accept \s-1BIO\s0,
257that is the chain will be accept->otherbios->socket.
258.PP
259If a server wishes to process multiple connections (as is normally
260the case) then the accept \s-1BIO\s0 must be made available for further
261incoming connections. This can be done by waiting for a connection and
262then calling:
263.PP
264.Vb 1
265\& connection = BIO_pop(accept);
266.Ve
267After this call \fBconnection\fR will contain a \s-1BIO\s0 for the recently
268established connection and \fBaccept\fR will now be a single \s-1BIO\s0
269again which can be used to await further incoming connections.
270If no further connections will be accepted the \fBaccept\fR can
271be freed using \fIBIO_free()\fR.
272.PP
273If only a single connection will be processed it is possible to
274perform I/O using the accept \s-1BIO\s0 itself. This is often undesirable
275however because the accept \s-1BIO\s0 will still accept additional incoming
276connections. This can be resolved by using \fIBIO_pop()\fR (see above)
277and freeing up the accept \s-1BIO\s0 after the initial connection.
278.PP
279If the underlying accept socket is non-blocking and \fIBIO_do_accept()\fR is
280called to await an incoming connection it is possible for
281\&\fIBIO_should_io_special()\fR with the reason \s-1BIO_RR_ACCEPT\s0. If this happens
282then it is an indication that an accept attempt would block: the application
283should take appropriate action to wait until the underlying socket has
284accepted a connection and retry the call.
285.PP
286\&\fIBIO_set_accept_port()\fR, \fIBIO_get_accept_port()\fR, \fIBIO_set_nbio_accept()\fR,
287\&\fIBIO_set_accept_bios()\fR, \fIBIO_set_bind_mode()\fR, \fIBIO_get_bind_mode()\fR and
288\&\fIBIO_do_accept()\fR are macros.
289.SH "RETURN VALUES"
290.IX Header "RETURN VALUES"
291\&\s-1TBA\s0
292.SH "EXAMPLE"
293.IX Header "EXAMPLE"
294This example accepts two connections on port 4444, sends messages
295down each and finally closes both down.
296.PP
297.Vb 3
298\& BIO *abio, *cbio, *cbio2;
299\& ERR_load_crypto_strings();
300\& abio = BIO_new_accept("4444");
301.Ve
302.Vb 6
303\& /* First call to BIO_accept() sets up accept BIO */
304\& if(BIO_do_accept(abio) <= 0) {
305\& fprintf(stderr, "Error setting up accept\en");
306\& ERR_print_errors_fp(stderr);
307\& exit(0);
308\& }
309.Ve
310.Vb 23
311\& /* Wait for incoming connection */
312\& if(BIO_do_accept(abio) <= 0) {
313\& fprintf(stderr, "Error accepting connection\en");
314\& ERR_print_errors_fp(stderr);
315\& exit(0);
316\& }
317\& fprintf(stderr, "Connection 1 established\en");
318\& /* Retrieve BIO for connection */
319\& cbio = BIO_pop(abio);
320\& BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\en");
321\& fprintf(stderr, "Sent out data on connection 1\en");
322\& /* Wait for another connection */
323\& if(BIO_do_accept(abio) <= 0) {
324\& fprintf(stderr, "Error accepting connection\en");
325\& ERR_print_errors_fp(stderr);
326\& exit(0);
327\& }
328\& fprintf(stderr, "Connection 2 established\en");
329\& /* Close accept BIO to refuse further connections */
330\& cbio2 = BIO_pop(abio);
331\& BIO_free(abio);
332\& BIO_puts(cbio2, "Connection 2: Sending out Data on second\en");
333\& fprintf(stderr, "Sent out data on connection 2\en");
334.Ve
335.Vb 4
336\& BIO_puts(cbio, "Connection 1: Second connection established\en");
337\& /* Close the two established connections */
338\& BIO_free(cbio);
339\& BIO_free(cbio2);
340.Ve
341.SH "SEE ALSO"
342.IX Header "SEE ALSO"
343\&\s-1TBA\s0