1BIO_s_accept(3) OpenSSL BIO_s_accept(3)
2
6 BIO_s_accept, BIO_set_accept_port, BIO_get_accept_port,
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 trans‐
37 ferred using only BIO routines. In this way any platform specific oper‐
38 ations 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 con‐
43 nection.
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 connec‐
52 tion.
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. Either or both values
60 can be "*" which is interpreted as meaning any interface or port
61 respectively. "port" has the same syntax as the port specified in
62 BIO_set_conn_port() for connect BIOs, that is it can be a numerical
63 port string or a string to lookup using getservbyname() and a string
64 table.
65 BIO_new_accept() combines BIO_new() and BIO_set_accept_port() into a
67 single call: that is it creates a new accept BIO with port host_port.
68 BIO_set_nbio_accept() sets the accept socket to blocking mode (the
70 default) if n is 0 or non blocking mode if n is 1.
71 BIO_set_accept_bios() can be used to set a chain of BIOs which will be
73 duplicated and prepended to the chain when an incoming connection is
74 received. This is useful if, for example, a buffering or SSL BIO is
75 required for each connection. The chain of BIOs must not be freed after
76 this call, they will be automatically freed when the accept BIO is
77 freed.
78 BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve the cur‐
80 rent bind mode. If BIO_BIND_NORMAL (the default) is set then another
81 socket cannot be bound to the same port. If BIO_BIND_REUSEADDR is set
82 then other sockets can bind to the same port. If BIO_BIND_REUSE‐
83 ADDR_IF_UNUSED is set then and attempt is first made to use
84 BIO_BIN_NORMAL, if this fails and the port is not in use then a second
85 attempt is made using BIO_BIND_REUSEADDR.
86 BIO_do_accept() serves two functions. When it is first called, after
88 the accept BIO has been setup, it will attempt to create the accept
89 socket and bind an address to it. Second and subsequent calls to
90 BIO_do_accept() will await an incoming connection, or request a retry
91 in non blocking mode.
92
94 When an accept BIO is at the end of a chain it will await an incoming
95 connection before processing I/O calls. When an accept BIO is not at
96 then end of a chain it passes I/O calls to the next BIO in the chain.
97 When a connection is established a new socket BIO is created for the
99 connection and appended to the chain. That is the chain is now
100 accept->socket. This effectively means that attempting I/O on an ini‐
101 tial accept socket will await an incoming connection then perform I/O
102 on it.
103 If any additional BIOs have been set using BIO_set_accept_bios() then
105 they are placed between the socket and the accept BIO, that is the
106 chain will be accept->otherbios->socket.
107 If a server wishes to process multiple connections (as is normally the
109 case) then the accept BIO must be made available for further incoming
110 connections. This can be done by waiting for a connection and then
111 calling:
112 connection = BIO_pop(accept);
114 After this call connection will contain a BIO for the recently estab‐
116 lished connection and accept will now be a single BIO again which can
117 be used to await further incoming connections. If no further connec‐
118 tions will be accepted the accept can be freed using BIO_free().
119 If only a single connection will be processed it is possible to perform
121 I/O using the accept BIO itself. This is often undesirable however
122 because the accept BIO will still accept additional incoming connec‐
123 tions. This can be resolved by using BIO_pop() (see above) and freeing
124 up the accept BIO after the initial connection.
125 If the underlying accept socket is non-blocking and BIO_do_accept() is
127 called to await an incoming connection it is possible for
128 BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens
129 then it is an indication that an accept attempt would block: the appli‐
130 cation should take appropriate action to wait until the underlying
131 socket has accepted a connection and retry the call.
132 BIO_set_accept_port(), BIO_get_accept_port(), BIO_set_nbio_accept(),
134 BIO_set_accept_bios(), BIO_set_bind_mode(), BIO_get_bind_mode() and
135 BIO_do_accept() are macros.
136
138 TBA
139
141 This example accepts two connections on port 4444, sends messages down
142 each and finally closes both down.
143 BIO *abio, *cbio, *cbio2;
145 ERR_load_crypto_strings();
146 abio = BIO_new_accept("4444");
147 /* First call to BIO_accept() sets up accept BIO */
149 if(BIO_do_accept(abio) <= 0) {
150 fprintf(stderr, "Error setting up accept\n");
151 ERR_print_errors_fp(stderr);
152 exit(0);
153 }
154 /* Wait for incoming connection */
156 if(BIO_do_accept(abio) <= 0) {
157 fprintf(stderr, "Error accepting connection\n");
158 ERR_print_errors_fp(stderr);
159 exit(0);
160 }
161 fprintf(stderr, "Connection 1 established\n");
162 /* Retrieve BIO for connection */
163 cbio = BIO_pop(abio);
164 BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
165 fprintf(stderr, "Sent out data on connection 1\n");
166 /* Wait for another connection */
167 if(BIO_do_accept(abio) <= 0) {
168 fprintf(stderr, "Error accepting connection\n");
169 ERR_print_errors_fp(stderr);
170 exit(0);
171 }
172 fprintf(stderr, "Connection 2 established\n");
173 /* Close accept BIO to refuse further connections */
174 cbio2 = BIO_pop(abio);
175 BIO_free(abio);
176 BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
177 fprintf(stderr, "Sent out data on connection 2\n");
178 BIO_puts(cbio, "Connection 1: Second connection established\n");
180 /* Close the two established connections */
181 BIO_free(cbio);
182 BIO_free(cbio2);
183
185 TBA
1860.9.8b 2002-12-12 BIO_s_accept(3)