=pod =head1 NAME SSL_write - write bytes to a TLS/SSL connection. =head1 SYNOPSIS #include int SSL_write(SSL *ssl, const void *buf, int num); =head1 DESCRIPTION SSL_write() writes B bytes from the buffer B into the specified B connection. =head1 NOTES If necessary, SSL_write() will negotiate a TLS/SSL session, if not already explicitly performed by L or L. If the peer requests a re-negotiation, it will be performed transparently during the SSL_write() operation. The behaviour of SSL_write() depends on the underlying BIO. For the transparent negotiation to succeed, the B must have been initialized to client or server mode. This is being done by calling L or SSL_set_accept_state() before the first call to an L or SSL_write() function. If the underlying BIO is B, SSL_write() will only return, once the write operation has been finished or an error occurred, except when a renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur. This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the L call. If the underlying BIO is B, SSL_write() will also return, when the underlying BIO could not satisfy the needs of SSL_write() to continue the operation. In this case a call to L with the return value of SSL_write() will yield B or B. As at any time a re-negotiation is possible, a call to SSL_write() can also cause read operations! The calling process then must repeat the call after taking appropriate action to satisfy the needs of SSL_write(). 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. SSL_write() will only return with success, when the complete contents of B of length B has been written. This default behaviour can be changed with the SSL_MODE_ENABLE_PARTIAL_WRITE option of L. When this flag is set, SSL_write() will also return with success, when a partial write has been successfully completed. In this case the SSL_write() operation is considered completed. The bytes are sent and a new SSL_write() operation 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 for SSLv3/TLSv1. =head1 WARNING When an SSL_write() operation has to be repeated because of B or B, it must be repeated with the same arguments. When calling SSL_write() with num=0 bytes to be sent the behaviour is undefined. =head1 RETURN VALUES The following return values can occur: =over 4 =item E0 The write operation was successful, the return value is the number of bytes actually written to the TLS/SSL connection. =item 0 The write operation was not successful. Probably the underlying connection was closed. Call SSL_get_error() with the return value B to find out, whether an error occurred or the connection was shut down cleanly (SSL_ERROR_ZERO_RETURN). SSLv2 (deprecated) does not support a shutdown alert protocol, so it can only be detected, whether the underlying connection was closed. It cannot be checked, why the closure happened. =item E0 The write operation was not successful, because either an error occurred or action must be taken by the calling process. Call SSL_get_error() with the return value B to find out the reason. =back =head1 SEE ALSO L, L, L, L, L, L L, L, L =cut d='n37' href='#n37'>37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217