1SSL_do_handshake(3)                 OpenSSL                SSL_do_handshake(3)
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NAME

6       SSL_do_handshake - perform a TLS/SSL handshake
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SYNOPSIS

9        #include <openssl/ssl.h>
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11        int SSL_do_handshake(SSL *ssl);
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DESCRIPTION

14       SSL_do_handshake() will wait for a SSL/TLS handshake to take place. If
15       the connection is in client mode, the handshake will be started. The
16       handshake routines may have to be explicitly set in advance using
17       either SSL_set_connect_state(3) or SSL_set_accept_state(3).
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NOTES

20       The behaviour of SSL_do_handshake() depends on the underlying BIO.
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22       If the underlying BIO is blocking, SSL_do_handshake() will only return
23       once the handshake has been finished or an error occurred.
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25       If the underlying BIO is non-blocking, SSL_do_handshake() will also
26       return when the underlying BIO could not satisfy the needs of
27       SSL_do_handshake() to continue the handshake. In this case a call to
28       SSL_get_error() with the return value of SSL_do_handshake() will yield
29       SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE. The calling process then
30       must repeat the call after taking appropriate action to satisfy the
31       needs of SSL_do_handshake().  The action depends on the underlying BIO.
32       When using a non-blocking socket, nothing is to be done, but select()
33       can be used to check for the required condition. When using a buffering
34       BIO, like a BIO pair, data must be written into or retrieved out of the
35       BIO before being able to continue.
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RETURN VALUES

38       The following return values can occur:
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40       0   The TLS/SSL handshake was not successful but was shut down
41           controlled and by the specifications of the TLS/SSL protocol. Call
42           SSL_get_error() with the return value ret to find out the reason.
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44       1   The TLS/SSL handshake was successfully completed, a TLS/SSL
45           connection has been established.
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47       <0  The TLS/SSL handshake was not successful because a fatal error
48           occurred either at the protocol level or a connection failure
49           occurred. The shutdown was not clean. It can also occur of action
50           is need to continue the operation for non-blocking BIOs. Call
51           SSL_get_error() with the return value ret to find out the reason.
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SEE ALSO

54       SSL_get_error(3), SSL_connect(3), SSL_accept(3), ssl(3), bio(3),
55       SSL_set_connect_state(3)
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591.0.2o                            2020-08-01               SSL_do_handshake(3)
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