=pod

=head1 NAME

SSL_accept - Wait for a TLS client to initiate a TLS handshake

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_accept(SSL *ssl);

=head1 DESCRIPTION

SSL_accept() waits for a TLS client to initiate the TLS handshake.
The communication channel must already have been set and assigned to the
B<ssl> by setting an underlying B<BIO>. The behaviour of SSL_accept() depends
on the underlying BIO. 

If the underlying BIO is B<blocking>, SSL_accept() will only return, once the
handshake has been finished or an error occured, except for SGC (Server
Gated Cryptography). For SGC SSL_accept() may return with -1 but
SSL_get_error() will yield SSL_ERROR_WANT_READ/WRITE and SSL_accept()
should be called again.

If the underlying BIO is B<non-blocking>, SSL_accept() will also return,
when the underlying BIO could not satisfy the needs of SSL_accept()
to continue the handshake. In this case a call to SSL_get_error() with the
return value of SSL_accept() will yield SSL_ERROR_WANT_READ or
SSL_ERROR_WANT_WRITE. The calling process then must repeat the call after
taking appropriate action to satisfy the needs of SSL_accept().
The action depends on the underlying BIO. When using a non-blocking socket,
nothing is to be done, but select() can be used to check for the required
condition. When using a buffering BIO, like a BIO pair, data must be written
into or retrieved out of the BIO before being able to continue.

=head1 RETURN VALUES

The following return values can occur:

=over 4

=item 1

The TLS handshake was successfully completed, a TLS connection has been
established.

=item 0

The TLS handshake was not successfull but was shut down controlled and
by the specifications of the TLS protocol. Call SSL_get_error() with the
return value B<ret> to find out the reason.

=item -1

The TLS handshake was not successfull, because a fatal error occured either
at the protocol level or a connection failure occured. The shutdown was
not clean. It can also occure of action is need to continue the operation
for non-blocking BIOs. Call SSL_get_error() with the return value B<ret>
to find out the reason.

=back

=head1 SEE ALSO

L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_connect(3)|SSL_connect(3)>,
L<SSL_shutdown(3)|SSL_shutdown(3)>, L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>

=cut