BIO_s_accept(3)BIO_s_accept(3)NAME
BIO_s_accept, BIO_set_accept_port, BIO_get_accept_port,
BIO_set_nbio_accept, BIO_set_accept_bios, BIO_set_bind_mode,
BIO_get_bind_mode, BIO_do_accept - Accept BIO
SYNOPSIS
#include <openssl/bio.h>
BIO_METHOD * BIO_s_accept(
void ); #define BIO_set_accept_port(b,name)
BIO_ctrl(b,BIO_C_SET_ACCEPT,0,(char *)name) #define
BIO_get_accept_port(b) BIO_ptr_ctrl(b,BIO_C_GET_ACCEPT,0)
BIO *BIO_new_accept(
char *host_port ); #define BIO_set_nbio_accept(b,n)
BIO_ctrl(b,BIO_C_SET_ACCEPT,1,(n)?"a":NULL) #define
BIO_set_accept_bios(b,bio) BIO_ctrl(b,BIO_C_SET_ACCEPT,2,(char *)bio)
#define BIO_set_bind_mode(b,mode)
BIO_ctrl(b,BIO_C_SET_BIND_MODE,mode,NULL) #define
BIO_get_bind_mode(b,mode) BIO_ctrl(b,BIO_C_GET_BIND_MODE,0,NULL)
#define BIO_BIND_NORMAL 0 #define BIO_BIND_REUSE‐
ADDR_IF_UNUSED 1 #define BIO_BIND_REUSEADDR 2
#define BIO_do_accept(b)BIO_do_handshake(b)DESCRIPTION
The BIO_s_accept() function returns the accept BIO method. This is a
wrapper round the platform's TCP/IP socket accept routines.
Using accept BIOs, TCP/IP connections can be accepted and data trans‐
ferred using only BIO routines. In this way any platform specific oper‐
ations are hidden by the BIO abstraction.
Read and write operations on an accept BIO will perform I/O on the
underlying connection. If no connection is established and the port is
set up properly then the BIO waits for an incoming connection.
Accept BIOs support BIO_puts() but not BIO_gets().
If the close option is set on an accept BIO then any active connection
on that chain is shutdown and the socket closed when the BIO is freed.
Calling BIO_reset() on a accept BIO will close any active connection
and reset the BIO into a state where it awaits another incoming connec‐
tion.
The BIO_get_fd() and BIO_set_fd() functions can be called to retrieve
or set the accept socket. See BIO_s_fd(3)BIO_set_accept_port() uses the string name to set the accept port. The
port is represented as a string of the form host:port, where host is
the interface to use and port is the port. Either or both values can be
* which is interpreted as meaning any interface or port respectively.
Port has the same syntax as the port specified in BIO_set_conn_port()
for connect BIOs; it can be a numerical port string or a string to
lookup using getservbyname() and a string table.
BIO_new_accept() combines BIO_new() and BIO_set_accept_port() into a
single call; it creates a new accept BIO with port host_port.
BIO_set_nbio_accept() sets the accept socket to blocking mode (the
default) if n is 0 or nonblocking mode if n is 1.
The BIO_set_accept_bios() function can be used to set a chain of BIOs
which will be duplicated and prepended to the chain when an incoming
connection is received. This is useful if, for example, a buffering or
SSL BIO is required for each connection. The chain of BIOs must not be
freed after this call. They will be automatically freed when the accept
BIO is freed.
The BIO_set_bind_mode() and BIO_get_bind_mode() functions set and
retrieve the current bind mode. If BIO_BIND_NORMAL (the default) is
set, then another socket cannot be bound to the same port. If
BIO_BIND_REUSEADDR is set, then other sockets can bind to the same
port. If BIO_BIND_REUSEADDR_IF_UNUSED is set, then an attempt is first
made to use BIO_BIN_NORMAL. If this fails and the port is not in use,
then a second attempt is made using BIO_BIND_REUSEADDR.
BIO_do_accept() serves two functions. When it is first called, after
the accept BIO has been setup, it will attempt to create the accept
socket and bind an address to it. Second and subsequent calls to
BIO_do_accept() will await an incoming connection.
NOTES
When an accept BIO is at the end of a chain it will await an incoming
connection before processing I/O calls. When an accept BIO is not at
then end of a chain it passes I/O calls to the next BIO in the chain.
When a connection is established a new socket BIO is created for the
connection and appended to the chain. The chain is now accept->socket.
This effectively means that attempting I/O on an initial accept socket
will await an incoming connection then perform I/O on it.
If any additional BIOs have been set using the BIO_set_accept_bios()
function then they are placed between the socket and the accept BIO.
The chain will be accept->otherbios->socket.
If a server wishes to process multiple connections (as is normally the
case), then the accept BIO must be made available for further incoming
connections. This can be done by waiting for a connection and then
calling:
connection = BIO_pop(accept);
After this call, connection will contain a BIO for the recently estab‐
lished connection and accept will be a single BIO again which can be
used to await further incoming connections. If no further connections
will be accepted, the accept can be freed using the BIO_free() func‐
tion.
If only a single connection will be processed it is possible to perform
I/O using the accept BIO. This is often undesirable however because the
accept BIO will still accept additional incoming connections. This can
be resolved by using the BIO_pop() function and freeing up the accept
BIO after the initial connection.
RETURN VALUES
TBA
EXAMPLES
This example accepts two connections on port 4444, sends messages down
each and finally closes both down.
BIO *abio, *cbio, *cbio2;
ERR_load_crypto_strings();
abio = BIO_new_accept("4444");
/* First call to BIO_accept() sets up accept BIO */
if(BIO_do_accept(abio) <= 0) { fprintf(stderr, "Error setting up
accept\n"); ERR_print_errors_fp(stderr); exit(0);
}
/* Wait for incoming connection */
if(BIO_do_accept(abio) <= 0) { fprintf(stderr, "Error accepting
connection\n"); ERR_print_errors_fp(stderr); exit(0);
}
fprintf(stderr, "Connection 1 established\n");
/* Retrieve BIO for connection */
cbio = BIO_pop(abio);
BIO_puts(cbio, "Connection 1: Sending out Data on initial connec‐
tion\n");
fprintf(stderr, "Sent out data on connection 1\n");
/* Wait for another connection */
if(BIO_do_accept(abio) <= 0) { fprintf(stderr, "Error accepting
connection\n"); ERR_print_errors_fp(stderr); exit(0);
}
fprintf(stderr, "Connection 2 established\n");
/* Close accept BIO to refuse further connections */
cbio2 = BIO_pop(abio);
BIO_free(abio);
BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
fprintf(stderr, "Sent out data on connection 2\n");
BIO_puts(cbio, "Connection 1: Second connection established\n");
/* Close the two established connections */
BIO_free(cbio);
BIO_free(cbio2);
SEE ALSO
TBA
BIO_s_accept(3)