SSL_connect(3)

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 commu-
       nication 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 con-
           trolled 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 connec-
           tion 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)

1.0.2t                            2019-09-10                    SSL_connect(3)