5 SSL_read - 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
16 B<ssl>. If necessary, SSL_write() will negotiate a TLS/SSL session, if
17 not already explicitly performed by SSL_connect() or SSL_accept(). If the
18 peer requests a re-negotiation, it will be performed transparently during
19 the SSL_write() operation. The behaviour of SSL_write() depends on the
22 If the underlying BIO is B<blocking>, SSL_write() will only return, once the
23 write operation has been finished or an error occurred.
25 If the underlying BIO is B<non-blocking>, SSL_write() will also return,
26 when the underlying BIO could not satisfy the needs of SSL_write()
27 to continue the operation. In this case a call to SSL_get_error() with the
28 return value of SSL_write() will yield B<SSL_ERROR_WANT_READ> or
29 B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
30 call to SSL_write() can also cause write operations! The calling process
31 then must repeat the call after taking appropriate action to satisfy the
32 needs of SSL_write(). The action depends on the underlying BIO. When using a
33 non-blocking socket, nothing is to be done, but select() can be used to check
34 for the required condition. When using a buffering BIO, like a BIO pair, data
35 must be written into or retrieved out of the BIO before being able to continue.
39 The following return values can occur:
45 The write operation was successful, the return value is the number of
46 bytes actually written to the TLS/SSL connection.
50 The write operation was not successful. Call SSL_get_error() with the return
51 value B<ret> to find out, whether an error occurred.
55 The read operation was not successful, because either an error occurred
56 or action must be taken by the calling process. Call SSL_get_error() with the
57 return value B<ret> to find out the reason.
63 L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_read(3)|SSL_read(3)>,
64 L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>