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.
29 If the underlying BIO is B<non-blocking>, SSL_write() will also return,
30 when the underlying BIO could not satisfy the needs of SSL_write()
31 to continue the operation. In this case a call to SSL_get_error() with the
32 return value of SSL_write() will yield B<SSL_ERROR_WANT_READ> or
33 B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
34 call to SSL_write() can also cause read operations! The calling process
35 then must repeat the call after taking appropriate action to satisfy the
36 needs of SSL_write(). The action depends on the underlying BIO. When using a
37 non-blocking socket, nothing is to be done, but select() can be used to check
38 for the required condition. When using a buffering BIO, like a BIO pair, data
39 must be written into or retrieved out of the BIO before being able to continue.
43 When an SSL_write() operation has to be repeated because of
44 B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
45 with the same arguments.
49 The following return values can occur:
55 The write operation was successful, the return value is the number of
56 bytes actually written to the TLS/SSL connection.
60 The write operation was not successful. Call SSL_get_error() with the return
61 value B<ret> to find out, whether an error occurred.
65 The write operation was not successful, because either an error occurred
66 or action must be taken by the calling process. Call SSL_get_error() with the
67 return value B<ret> to find out the reason.
73 L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_read(3)|SSL_read(3)>,
74 L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>