NAME

       SSL_connect - initiate the TLS/SSL handshake with an TLS/SSL server

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_connect(SSL *ssl);

DESCRIPTION

       SSL_connect() initiates the TLS/SSL handshake with a server. The communication channel
       must already have been set and assigned to the ssl by setting an underlying BIO.

NOTES

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

       If the underlying BIO is blocking, SSL_connect() will only return once the handshake has
       been finished or an error occurred.

       If the underlying BIO is non-blocking, SSL_connect() will also return when the underlying
       BIO could not satisfy the needs of SSL_connect() 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_connect() 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_connect().  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_accept(3), SSL_shutdown(3), ssl(3), bio(3),
       SSL_set_connect_state(3), SSL_do_handshake(3), SSL_CTX_new(3)