NAME

       SSL_accept - wait for a TLS/SSL client to initiate a TLS/SSL handshake

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_accept(SSL *ssl);

DESCRIPTION

       SSL_accept() waits for a TLS/SSL client to initiate the TLS/SSL handshake.  The
       communication channel must already have been set and assigned to the ssl by setting an
       underlying BIO.

NOTES

       The behaviour of SSL_accept() depends on the underlying BIO.

       If the underlying BIO is blocking, SSL_accept() will only return once the handshake has
       been finished or an error occurred, 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 non-blocking, SSL_accept() will also return when the underlying
       BIO could not satisfy the needs of SSL_accept() to continue the handshake, indicating the
       problem by the return value -1.  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.

RETURN VALUES

       The following return values can occur:

       0   The TLS/SSL handshake was not successful but was shut down controlled and by the
           specifications of the TLS/SSL protocol. Call SSL_get_error() with the return value ret
           to find out the reason.

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

       <0  The TLS/SSL handshake was not successful because a fatal error occurred either at the
           protocol level or a connection failure occurred. The shutdown was not clean. It can
           also occur of action is need to continue the operation for non-blocking BIOs. Call
           SSL_get_error() with the return value ret to find out the reason.

SEE ALSO

       SSL_get_error(3), SSL_connect(3), SSL_shutdown(3), ssl(3), bio(3),
       SSL_set_connect_state(3), SSL_do_handshake(3), SSL_CTX_new(3)