1BIO_s_accept(3) OpenSSL BIO_s_accept(3)
2
6 BIO_s_accept, BIO_set_accept_port, BIO_get_accept_port, BIO_new_accept,
7 BIO_set_nbio_accept, BIO_set_accept_bios, BIO_set_bind_mode,
8 BIO_get_bind_mode, BIO_do_accept - accept BIO
9
11 #include <openssl/bio.h>
12 BIO_METHOD *BIO_s_accept(void);
14 long BIO_set_accept_port(BIO *b, char *name);
16 char *BIO_get_accept_port(BIO *b);
17 BIO *BIO_new_accept(char *host_port);
19 long BIO_set_nbio_accept(BIO *b, int n);
21 long BIO_set_accept_bios(BIO *b, char *bio);
22 long BIO_set_bind_mode(BIO *b, long mode);
24 long BIO_get_bind_mode(BIO *b, long dummy);
25 #define BIO_BIND_NORMAL 0
27 #define BIO_BIND_REUSEADDR_IF_UNUSED 1
28 #define BIO_BIND_REUSEADDR 2
29 int BIO_do_accept(BIO *b);
31
33 BIO_s_accept() returns the accept BIO method. This is a wrapper round
34 the platform's TCP/IP socket accept routines.
35 Using accept BIOs, TCP/IP connections can be accepted and data
37 transferred using only BIO routines. In this way any platform specific
38 operations are hidden by the BIO abstraction.
39 Read and write operations on an accept BIO will perform I/O on the
41 underlying connection. If no connection is established and the port
42 (see below) is set up properly then the BIO waits for an incoming
43 connection.
44 Accept BIOs support BIO_puts() but not BIO_gets().
46 If the close flag is set on an accept BIO then any active connection on
48 that chain is shutdown and the socket closed when the BIO is freed.
49 Calling BIO_reset() on a accept BIO will close any active connection
51 and reset the BIO into a state where it awaits another incoming
52 connection.
53 BIO_get_fd() and BIO_set_fd() can be called to retrieve or set the
55 accept socket. See BIO_s_fd(3)
56 BIO_set_accept_port() uses the string name to set the accept port. The
58 port is represented as a string of the form "host:port", where "host"
59 is the interface to use and "port" is the port. The host can be can be
60 "*" which is interpreted as meaning any interface; "port" has the same
61 syntax as the port specified in BIO_set_conn_port() for connect BIOs,
62 that is it can be a numerical port string or a string to lookup using
63 getservbyname() and a string table.
64 BIO_new_accept() combines BIO_new() and BIO_set_accept_port() into a
66 single call: that is it creates a new accept BIO with port host_port.
67 BIO_set_nbio_accept() sets the accept socket to blocking mode (the
69 default) if n is 0 or non blocking mode if n is 1.
70 BIO_set_accept_bios() can be used to set a chain of BIOs which will be
72 duplicated and prepended to the chain when an incoming connection is
73 received. This is useful if, for example, a buffering or SSL BIO is
74 required for each connection. The chain of BIOs must not be freed after
75 this call, they will be automatically freed when the accept BIO is
76 freed.
77 BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve the
79 current bind mode. If BIO_BIND_NORMAL (the default) is set then another
80 socket cannot be bound to the same port. If BIO_BIND_REUSEADDR is set
81 then other sockets can bind to the same port. If
82 BIO_BIND_REUSEADDR_IF_UNUSED is set then and attempt is first made to
83 use BIO_BIN_NORMAL, if this fails and the port is not in use then a
84 second attempt is made using BIO_BIND_REUSEADDR.
85 BIO_do_accept() serves two functions. When it is first called, after
87 the accept BIO has been setup, it will attempt to create the accept
88 socket and bind an address to it. Second and subsequent calls to
89 BIO_do_accept() will await an incoming connection, or request a retry
90 in non blocking mode.
91
93 When an accept BIO is at the end of a chain it will await an incoming
94 connection before processing I/O calls. When an accept BIO is not at
95 then end of a chain it passes I/O calls to the next BIO in the chain.
96 When a connection is established a new socket BIO is created for the
98 connection and appended to the chain. That is the chain is now
99 accept->socket. This effectively means that attempting I/O on an
100 initial accept socket will await an incoming connection then perform
101 I/O on it.
102 If any additional BIOs have been set using BIO_set_accept_bios() then
104 they are placed between the socket and the accept BIO, that is the
105 chain will be accept->otherbios->socket.
106 If a server wishes to process multiple connections (as is normally the
108 case) then the accept BIO must be made available for further incoming
109 connections. This can be done by waiting for a connection and then
110 calling:
111 connection = BIO_pop(accept);
113 After this call connection will contain a BIO for the recently
115 established connection and accept will now be a single BIO again which
116 can be used to await further incoming connections. If no further
117 connections will be accepted the accept can be freed using BIO_free().
118 If only a single connection will be processed it is possible to perform
120 I/O using the accept BIO itself. This is often undesirable however
121 because the accept BIO will still accept additional incoming
122 connections. This can be resolved by using BIO_pop() (see above) and
123 freeing up the accept BIO after the initial connection.
124 If the underlying accept socket is non-blocking and BIO_do_accept() is
126 called to await an incoming connection it is possible for
127 BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens
128 then it is an indication that an accept attempt would block: the
129 application should take appropriate action to wait until the underlying
130 socket has accepted a connection and retry the call.
131 BIO_set_accept_port(), BIO_get_accept_port(), BIO_set_nbio_accept(),
133 BIO_set_accept_bios(), BIO_set_bind_mode(), BIO_get_bind_mode() and
134 BIO_do_accept() are macros.
135
137 TBA
138
140 This example accepts two connections on port 4444, sends messages down
141 each and finally closes both down.
142 BIO *abio, *cbio, *cbio2;
144 ERR_load_crypto_strings();
145 abio = BIO_new_accept("4444");
146 /* First call to BIO_accept() sets up accept BIO */
148 if(BIO_do_accept(abio) <= 0) {
149 fprintf(stderr, "Error setting up accept\n");
150 ERR_print_errors_fp(stderr);
151 exit(0);
152 }
153 /* Wait for incoming connection */
155 if(BIO_do_accept(abio) <= 0) {
156 fprintf(stderr, "Error accepting connection\n");
157 ERR_print_errors_fp(stderr);
158 exit(0);
159 }
160 fprintf(stderr, "Connection 1 established\n");
161 /* Retrieve BIO for connection */
162 cbio = BIO_pop(abio);
163 BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
164 fprintf(stderr, "Sent out data on connection 1\n");
165 /* Wait for another connection */
166 if(BIO_do_accept(abio) <= 0) {
167 fprintf(stderr, "Error accepting connection\n");
168 ERR_print_errors_fp(stderr);
169 exit(0);
170 }
171 fprintf(stderr, "Connection 2 established\n");
172 /* Close accept BIO to refuse further connections */
173 cbio2 = BIO_pop(abio);
174 BIO_free(abio);
175 BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
176 fprintf(stderr, "Sent out data on connection 2\n");
177 BIO_puts(cbio, "Connection 1: Second connection established\n");
179 /* Close the two established connections */
180 BIO_free(cbio);
181 BIO_free(cbio2);
182
184 TBA
1851.0.2o 2020-01-28 BIO_s_accept(3)