5 BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port, BIO_get_accept_name,
6 BIO_get_accept_port, BIO_new_accept, BIO_set_nbio_accept, BIO_set_accept_bios,
7 BIO_get_peer_name, BIO_get_peer_port,
8 BIO_get_accept_ip_family, BIO_set_accept_ip_family,
9 BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept - accept BIO
13 #include <openssl/bio.h>
15 const BIO_METHOD *BIO_s_accept(void);
17 long BIO_set_accept_name(BIO *b, char *name);
18 char *BIO_get_accept_name(BIO *b);
20 long BIO_set_accept_port(BIO *b, char *port);
21 char *BIO_get_accept_port(BIO *b);
23 BIO *BIO_new_accept(char *host_port);
25 long BIO_set_nbio_accept(BIO *b, int n);
26 long BIO_set_accept_bios(BIO *b, char *bio);
28 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);
33 long BIO_set_bind_mode(BIO *b, long mode);
34 long BIO_get_bind_mode(BIO *b);
36 int BIO_do_accept(BIO *b);
40 BIO_s_accept() returns the accept BIO method. This is a wrapper
41 round the platform's TCP/IP socket accept routines.
43 Using accept BIOs, TCP/IP connections can be accepted and data
44 transferred using only BIO routines. In this way any platform
45 specific operations are hidden by the BIO abstraction.
47 Read and write operations on an accept BIO will perform I/O
48 on the underlying connection. If no connection is established
49 and the port (see below) is set up properly then the BIO
50 waits for an incoming connection.
52 Accept BIOs support BIO_puts() but not BIO_gets().
54 If the close flag is set on an accept BIO then any active
55 connection on that chain is shutdown and the socket closed when
58 Calling BIO_reset() on an accept BIO will close any active
59 connection and reset the BIO into a state where it awaits another
62 BIO_get_fd() and BIO_set_fd() can be called to retrieve or set
63 the accept socket. See L<BIO_s_fd(3)>
65 BIO_set_accept_name() uses the string B<name> to set the accept
66 name. The name is represented as a string of the form "host:port",
67 where "host" is the interface to use and "port" is the port.
68 The host can be "*" or empty which is interpreted as meaning
69 any interface. If the host is an IPv6 address, it has to be
70 enclosed in brackets, for example "[::1]:https". "port" has the
71 same syntax as the port specified in BIO_set_conn_port() for
72 connect BIOs, that is it can be a numerical port string or a
73 string to lookup using getservbyname() and a string table.
75 BIO_set_accept_port() uses the string B<port> to set the accept
76 port of BIO I<b>. "port" has the same syntax as the port specified in
77 BIO_set_conn_port() for connect BIOs, that is it can be a numerical
78 port string or a string to lookup using getservbyname() and a string
80 If the given port is C<0> then a random available port is chosen.
81 It may be queried using BIO_sock_info() and L<BIO_ADDR_service_string(3)>.
83 BIO_new_accept() combines BIO_new() and BIO_set_accept_name() into
84 a single call: that is it creates a new accept BIO with port
87 BIO_set_nbio_accept() sets the accept socket to blocking mode
88 (the default) if B<n> is 0 or non blocking mode if B<n> is 1.
90 BIO_set_accept_bios() can be used to set a chain of BIOs which
91 will be duplicated and prepended to the chain when an incoming
92 connection is received. This is useful if, for example, a
93 buffering or SSL BIO is required for each connection. The
94 chain of BIOs must not be freed after this call, they will
95 be automatically freed when the accept BIO is freed.
97 BIO_get_accept_ip_family() returns the IP family accepted by the BIO I<b>,
98 which may be B<BIO_FAMILY_IPV4>, B<BIO_FAMILY_IPV6>, or B<BIO_FAMILY_IPANY>.
100 BIO_set_accept_ip_family() sets the IP family I<family> accepted by BIO I<b>.
101 The default is B<BIO_FAMILY_IPANY>.
103 BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve
104 the current bind mode. If B<BIO_BIND_NORMAL> (the default) is set
105 then another socket cannot be bound to the same port. If
106 B<BIO_BIND_REUSEADDR> is set then other sockets can bind to the
107 same port. If B<BIO_BIND_REUSEADDR_IF_UNUSED> is set then and
108 attempt is first made to use BIO_BIN_NORMAL, if this fails
109 and the port is not in use then a second attempt is made
110 using B<BIO_BIND_REUSEADDR>.
112 BIO_do_accept() serves two functions. When it is first
113 called, after the accept BIO has been setup, it will attempt
114 to create the accept socket and bind an address to it. Second
115 and subsequent calls to BIO_do_accept() will await an incoming
116 connection, or request a retry in non blocking mode.
120 When an accept BIO is at the end of a chain it will await an
121 incoming connection before processing I/O calls. When an accept
122 BIO is not at then end of a chain it passes I/O calls to the next
125 When a connection is established a new socket BIO is created for
126 the connection and appended to the chain. That is the chain is now
127 accept->socket. This effectively means that attempting I/O on
128 an initial accept socket will await an incoming connection then
131 If any additional BIOs have been set using BIO_set_accept_bios()
132 then they are placed between the socket and the accept BIO,
133 that is the chain will be accept->otherbios->socket.
135 If a server wishes to process multiple connections (as is normally
136 the case) then the accept BIO must be made available for further
137 incoming connections. This can be done by waiting for a connection and
140 connection = BIO_pop(accept);
142 After this call B<connection> will contain a BIO for the recently
143 established connection and B<accept> will now be a single BIO
144 again which can be used to await further incoming connections.
145 If no further connections will be accepted the B<accept> can
146 be freed using BIO_free().
148 If only a single connection will be processed it is possible to
149 perform I/O using the accept BIO itself. This is often undesirable
150 however because the accept BIO will still accept additional incoming
151 connections. This can be resolved by using BIO_pop() (see above)
152 and freeing up the accept BIO after the initial connection.
154 If the underlying accept socket is nonblocking and BIO_do_accept() is
155 called to await an incoming connection it is possible for
156 BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens
157 then it is an indication that an accept attempt would block: the application
158 should take appropriate action to wait until the underlying socket has
159 accepted a connection and retry the call.
161 BIO_set_accept_name(), BIO_get_accept_name(), BIO_set_accept_port(),
162 BIO_get_accept_port(), BIO_set_nbio_accept(), BIO_set_accept_bios(),
163 BIO_get_peer_name(), BIO_get_peer_port(),
164 BIO_get_accept_ip_family(), BIO_set_accept_ip_family(),
165 BIO_set_bind_mode(), BIO_get_bind_mode() and BIO_do_accept() are macros.
170 BIO_set_accept_name(), BIO_set_accept_port(), BIO_set_nbio_accept(),
171 BIO_set_accept_bios(), BIO_set_accept_ip_family(), and BIO_set_bind_mode()
172 return 1 for success and <=0 for failure.
174 BIO_get_accept_name() returns the accept name or NULL on error.
175 BIO_get_peer_name() returns the peer name or NULL on error.
177 BIO_get_accept_port() returns the accept port as a string or NULL on error.
178 BIO_get_peer_port() returns the peer port as a string or NULL on error.
179 BIO_get_accept_ip_family() returns the IP family or <=0 on error.
181 BIO_get_bind_mode() returns the set of B<BIO_BIND> flags, or <=0 on failure.
183 BIO_new_accept() returns a BIO or NULL on error.
187 This example accepts two connections on port 4444, sends messages
188 down each and finally closes both down.
190 BIO *abio, *cbio, *cbio2;
192 /* First call to BIO_accept() sets up accept BIO */
193 abio = BIO_new_accept("4444");
194 if (BIO_do_accept(abio) <= 0) {
195 fprintf(stderr, "Error setting up accept\n");
196 ERR_print_errors_fp(stderr);
200 /* Wait for incoming connection */
201 if (BIO_do_accept(abio) <= 0) {
202 fprintf(stderr, "Error accepting connection\n");
203 ERR_print_errors_fp(stderr);
206 fprintf(stderr, "Connection 1 established\n");
208 /* Retrieve BIO for connection */
209 cbio = BIO_pop(abio);
210 BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
211 fprintf(stderr, "Sent out data on connection 1\n");
213 /* Wait for another connection */
214 if (BIO_do_accept(abio) <= 0) {
215 fprintf(stderr, "Error accepting connection\n");
216 ERR_print_errors_fp(stderr);
219 fprintf(stderr, "Connection 2 established\n");
221 /* Close accept BIO to refuse further connections */
222 cbio2 = BIO_pop(abio);
224 BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
225 fprintf(stderr, "Sent out data on connection 2\n");
227 BIO_puts(cbio, "Connection 1: Second connection established\n");
229 /* Close the two established connections */
235 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
237 Licensed under the Apache License 2.0 (the "License"). You may not use
238 this file except in compliance with the License. You can obtain a copy
239 in the file LICENSE in the source distribution or at
240 L<https://www.openssl.org/source/license.html>.