SSL_connect(3) — Subroutines

NAME

SSL_connect − Initiate the TLS/SSL handshake with an TLS/SSL server

SYNOPSIS

#include <openssl/ssl.h>
int SSL_connect(
SSL ∗ssl );

DESCRIPTION

The SSL_connect() function 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 behavior of the SSL_connect() function depends on the underlying BIO.

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

If the underlying BIO is non-blocking, the SSL_connect() function will also return when the underlying BIO could not satisfy the needs of SSL_connect() to continue the handshake. 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 the select() function 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:

1The TLS/SSL handshake was successfully completed. A TLS/SSL connection was established.

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

<0The 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 non-blocking BIOs. Call the SSL_get_error() function with the return value ret to find out the reason.

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