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BIO_S_ACCEPT(3)			    OpenSSL		       BIO_S_ACCEPT(3)

       BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port,
       BIO_get_accept_name, BIO_get_accept_port, BIO_new_accept,
       BIO_set_nbio_accept, BIO_set_accept_bios, BIO_get_peer_name,
       BIO_get_peer_port, BIO_get_accept_ip_family, BIO_set_accept_ip_family,
       BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept - accept BIO

	#include <openssl/bio.h>

	const BIO_METHOD *BIO_s_accept(void);

	long BIO_set_accept_name(BIO *b, char *name);
	char *BIO_get_accept_name(BIO *b);

	long BIO_set_accept_port(BIO *b, char *port);
	char *BIO_get_accept_port(BIO *b);

	BIO *BIO_new_accept(char *host_port);

	long BIO_set_nbio_accept(BIO *b, int n);
	long BIO_set_accept_bios(BIO *b, char *bio);

	char *BIO_get_peer_name(BIO *b);
	char *BIO_get_peer_port(BIO *b);
	long BIO_get_accept_ip_family(BIO *b);
	long BIO_set_accept_ip_family(BIO *b, long family);

	long BIO_set_bind_mode(BIO *b, long mode);
	long BIO_get_bind_mode(BIO *b);

	int BIO_do_accept(BIO *b);

       BIO_s_accept() 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
       transferred using only BIO routines. In this way	any platform specific
       operations 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
       (see below) is set up properly then the BIO waits for an	incoming

       Accept BIOs support BIO_puts() but not BIO_gets().

       If the close flag 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 an accept	BIO will close any active connection
       and reset the BIO into a	state where it awaits another incoming

       BIO_get_fd() and	BIO_set_fd() can be called to retrieve or set the
       accept socket. See BIO_s_fd(3)

       BIO_set_accept_name() uses the string name to set the accept name. The
       name is represented as a	string of the form "host:port",	where "host"
       is the interface	to use and "port" is the port.	The host can be	"*" or
       empty which is interpreted as meaning any interface.  If	the host is an
       IPv6 address, it	has to be enclosed in brackets,	for example
       "[::1]:https".  "port" has the same syntax as the port specified	in
       BIO_set_conn_port() for connect BIOs, that is it	can be a numerical
       port string or a	string to lookup using getservbyname() and a string

       BIO_set_accept_port() uses the string port to set the accept port.
       "port" has the same syntax as the port specified	in BIO_set_conn_port()
       for connect BIOs, that is 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_name() into a
       single call: that is 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 non blocking mode if n is 1.

       BIO_set_accept_bios() 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

       BIO_set_bind_mode() and BIO_get_bind_mode() 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	and 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, or request a retry
       in non blocking mode.

       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. That is 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 BIO_set_accept_bios()	then
       they are	placed between the socket and the accept BIO, that is 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

	connection = BIO_pop(accept);

       After this call connection will contain a BIO for the recently
       established connection and accept will now 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 BIO_free().

       If only a single	connection will	be processed it	is possible to perform
       I/O using the accept BIO	itself.	This is	often undesirable however
       because the accept BIO will still accept	additional incoming
       connections. This can be	resolved by using BIO_pop() (see above)	and
       freeing up the accept BIO after the initial connection.

       If the underlying accept	socket is non-blocking and BIO_do_accept() is
       called to await an incoming connection it is possible for
       BIO_should_io_special() with the	reason BIO_RR_ACCEPT. If this happens
       then it is an indication	that an	accept attempt would block: the
       application should take appropriate action to wait until	the underlying
       socket has accepted a connection	and retry the call.

       BIO_set_accept_name(), BIO_get_accept_name(), BIO_set_accept_port(),
       BIO_get_accept_port(), BIO_set_nbio_accept(), BIO_set_accept_bios(),
       BIO_get_peer_name(), BIO_get_peer_port(), BIO_get_accept_ip_family(),
       BIO_set_accept_ip_family(), BIO_set_bind_mode(),	BIO_get_bind_mode()
       and BIO_do_accept() are macros.

       BIO_do_accept(),	BIO_set_accept_name(), BIO_set_accept_port(),
       BIO_set_nbio_accept(), BIO_set_accept_bios(),
       BIO_set_accept_ip_family(), and BIO_set_bind_mode() return 1 for
       success and 0 or	-1 for failure.

       BIO_get_accept_name() returns the accept	name or	NULL on	error.
       BIO_get_peer_name() returns the peer name or NULL on error.

       BIO_get_accept_port() returns the accept	port as	a string or NULL on
       error.  BIO_get_peer_port() returns the peer port as a string or	NULL
       on error.  BIO_get_accept_ip_family() returns the IP family or -1 on

       BIO_get_bind_mode() returns the set of BIO_BIND flags, or -1 on

       BIO_new_accept()	returns	a BIO or NULL on error.

       This example accepts two	connections on port 4444, sends	messages down
       each and	finally	closes both down.

	BIO *abio, *cbio, *cbio2;

	/* First call to BIO_accept() sets up accept BIO */
	abio = BIO_new_accept("4444");
	if (BIO_do_accept(abio)	<= 0) {
	    fprintf(stderr, "Error setting up accept\n");

	/* Wait	for incoming connection	*/
	if (BIO_do_accept(abio)	<= 0) {
	    fprintf(stderr, "Error accepting connection\n");
	fprintf(stderr,	"Connection 1 established\n");

	/* Retrieve BIO	for connection */
	cbio = BIO_pop(abio);
	BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\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");
	fprintf(stderr,	"Connection 2 established\n");

	/* Close accept	BIO to refuse further connections */
	cbio2 =	BIO_pop(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 */

       Copyright 2000-2019 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at

1.1.1d				  2019-09-10		       BIO_S_ACCEPT(3)


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