SSL_ACCEPT(3SSL) OpenSSL SSL_ACCEPT(3SSL)
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.
If the underlying BIO is nonblocking, 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 nonblocking 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 if action is
needed to continue the operation for nonblocking 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(7), bio(7),
SSL_set_connect_state(3), SSL_do_handshake(3), SSL_CTX_new(3)
COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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
<https://www.openssl.org/source/license.html>.
3.5.7 2026-06-09 SSL_ACCEPT(3SSL)
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