SSL_CONNECT(3)             Library Functions Manual             SSL_CONNECT(3)

NAME
     SSL_connect - initiate the TLS/SSL handshake with a 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.

     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 with the return value -1.
     In this case a call to SSL_get_error(3) 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(2) 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(3) with the return value ret to find out the
             reason.

     1       The TLS/SSL handshake was successfully completed, and a TLS/SSL
             connection has been established.

     <0      The TLS/SSL handshake was not successful, because either a fatal
             error occurred 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 SSL_get_error(3) with the return value ret to find out the
             reason.

SEE ALSO
     BIO_new(3), ssl(3), SSL_accept(3), SSL_CTX_new(3), SSL_do_handshake(3),
     SSL_get_error(3), SSL_set_connect_state(3), SSL_shutdown(3)

HISTORY
     SSL_connect() appeared in SSLeay 0.4 or earlier and has been available
     since OpenBSD 2.4.

Linux 6.8.2-arch2-1             March 27, 2018             Linux 6.8.2-arch2-1