5 SSL_write - write bytes to a TLS/SSL connection.
9 #include <openssl/ssl.h>
11 int SSL_write(SSL *ssl, char *buf, int num);
15 SSL_write() writes B<num> bytes from the buffer B<buf> into the specified
20 If necessary, SSL_write() will negotiate a TLS/SSL session, if
21 not already explicitly performed by SSL_connect() or SSL_accept(). If the
22 peer requests a re-negotiation, it will be performed transparently during
23 the SSL_write() operation. The behaviour of SSL_write() depends on the
26 If the underlying BIO is B<blocking>, SSL_write() will only return, once the
27 write operation has been finished or an error occurred, except when a
28 renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
29 This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the
30 L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)> call.
32 If the underlying BIO is B<non-blocking>, SSL_write() will also return,
33 when the underlying BIO could not satisfy the needs of SSL_write()
34 to continue the operation. In this case a call to SSL_get_error() with the
35 return value of SSL_write() will yield B<SSL_ERROR_WANT_READ> or
36 B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
37 call to SSL_write() can also cause read operations! The calling process
38 then must repeat the call after taking appropriate action to satisfy the
39 needs of SSL_write(). The action depends on the underlying BIO. When using a
40 non-blocking socket, nothing is to be done, but select() can be used to check
41 for the required condition. When using a buffering BIO, like a BIO pair, data
42 must be written into or retrieved out of the BIO before being able to continue.
46 When an SSL_write() operation has to be repeated because of
47 B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
48 with the same arguments.
52 The following return values can occur:
58 The write operation was successful, the return value is the number of
59 bytes actually written to the TLS/SSL connection.
63 The write operation was not successful. Call SSL_get_error() with the return
64 value B<ret> to find out, whether an error occurred.
68 The write operation was not successful, because either an error occurred
69 or action must be taken by the calling process. Call SSL_get_error() with the
70 return value B<ret> to find out the reason.
76 L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_read(3)|SSL_read(3)>,
77 L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>,
78 L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>