- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- SEE ALSO

# 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:

1. 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.

2. 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, SSL_connect, SSL_shutdown, ssl, bio, SSL_set_connect_state, SSL_do_handshake, SSL_CTX_new