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SSL_WRITE(3)			    OpenSSL			  SSL_WRITE(3)

NAME
       SSL_write_ex, SSL_write - write bytes to	a TLS/SSL connection

SYNOPSIS
	#include <openssl/ssl.h>

	int SSL_write_ex(SSL *s, const void *buf, size_t num, size_t *written);
	int SSL_write(SSL *ssl,	const void *buf, int num);

DESCRIPTION
       SSL_write_ex() and SSL_write() write num	bytes from the buffer buf into
       the specified ssl connection. On	success	SSL_write_ex() will store the
       number of bytes written in *written.

NOTES
       In the paragraphs below a "write	function" is defined as	one of either
       SSL_write_ex(), or SSL_write().

       If necessary, a write function will negotiate a TLS/SSL session,	if not
       already explicitly performed by SSL_connect(3) or SSL_accept(3).	If the
       peer requests a re-negotiation, it will be performed transparently
       during the write	function operation. The	behaviour of the write
       functions depends on the	underlying BIO.

       For the transparent negotiation to succeed, the ssl must	have been
       initialized to client or	server mode. This is being done	by calling
       SSL_set_connect_state(3)	or SSL_set_accept_state() before the first
       call to a write function.

       If the underlying BIO is	blocking, the write functions will only
       return, once the	write operation	has been finished or an	error
       occurred.

       If the underlying BIO is	non-blocking the write functions will also
       return when the underlying BIO could not	satisfy	the needs of the
       function	to continue the	operation. In this case	a call to
       SSL_get_error(3)	with the return	value of the write function will yield
       SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE. As at any time a re-
       negotiation is possible,	a call to a write function can also cause read
       operations! The calling process then must repeat	the call after taking
       appropriate action to satisfy the needs of the write function. 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.

       The write functions will	only return with success when the complete
       contents	of buf of length num has been written. This default behaviour
       can be changed with the SSL_MODE_ENABLE_PARTIAL_WRITE option of
       SSL_CTX_set_mode(3). When this flag is set the write functions will
       also return with	success	when a partial write has been successfully
       completed. In this case the write function operation is considered
       completed. The bytes are	sent and a new write call with a new buffer
       (with the already sent bytes removed) must be started. A	partial	write
       is performed with the size of a message block, which is 16kB.

WARNINGS
       When a write function call has to be repeated because SSL_get_error(3)
       returned	SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE, it	must be
       repeated	with the same arguments.  The data that	was passed might have
       been partially processed.  When SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER was
       set using SSL_CTX_set_mode(3) the pointer can be	different, but the
       data and	length should still be the same.

       You should not call SSL_write() with num=0, it will return an error.
       SSL_write_ex() can be called with num=0,	but will not send application
       data to the peer.

RETURN VALUES
       SSL_write_ex() will return 1 for	success	or 0 for failure. Success
       means that all requested	application data bytes have been written to
       the SSL connection or, if SSL_MODE_ENABLE_PARTIAL_WRITE is in use, at
       least 1 application data	byte has been written to the SSL connection.
       Failure means that not all the requested	bytes have been	written	yet
       (if SSL_MODE_ENABLE_PARTIAL_WRITE is not	in use)	or no bytes could be
       written to the SSL connection (if SSL_MODE_ENABLE_PARTIAL_WRITE is in
       use). Failures can be retryable (e.g. the network write buffer has
       temporarily filled up) or non-retryable (e.g. a fatal network error).
       In the event of a failure call SSL_get_error(3) to find out the reason
       which indicates whether the call	is retryable or	not.

       For SSL_write() the following return values can occur:

       > 0 The write operation was successful, the return value	is the number
	   of bytes actually written to	the TLS/SSL connection.

       <= 0
	   The write operation was not successful, because either the
	   connection was closed, an error occurred or action must be taken by
	   the calling process.	 Call SSL_get_error() with the return value
	   ret to find out the reason.

	   Old documentation indicated a difference between 0 and -1, and that
	   -1 was retryable.  You should instead call SSL_get_error() to find
	   out if it's retryable.

SEE ALSO
       SSL_get_error(3), SSL_read_ex(3), SSL_read(3) SSL_CTX_set_mode(3),
       SSL_CTX_new(3), SSL_connect(3), SSL_accept(3) SSL_set_connect_state(3),
       ssl(7), bio(7)

HISTORY
       The SSL_write_ex() function was added in	OpenSSL	1.1.1.

COPYRIGHT
       Copyright 2000-2019 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

1.1.1d				  2019-09-10			  SSL_WRITE(3)

NAME | SYNOPSIS | DESCRIPTION | NOTES | WARNINGS | RETURN VALUES | SEE ALSO | HISTORY | COPYRIGHT

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