</code> is <code>NULL</code>. </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">will_message_size</td><td>The size of <code>will_message</code> in bytes. </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">user_name</td><td>The username to use when establishing the session with the MQTT broker. Set to <code>NULL</code> if a username is not required. </td></tr>
    <tr><td class="paramdir">[in]</td><td class="paramname">password</td><td>The password to use when establi