int mysql_ping(MYSQL *mysql)
Checks whether the connection to the server is working. If the
connection has gone down and auto-reconnect is enabled an
attempt to reconnect is made. If the connection is down and
auto-reconnect is disabled,
mysql_ping() returns an error.
mysql_ping() can be used by
clients that remain idle for a long while, to check whether
the server has closed the connection and reconnect if
mysql_ping()) does cause a
reconnect, there is no explicit indication of it. To determine
whether a reconnect occurs, call
mysql_thread_id() to get the
original connection identifier before calling
mysql_ping(), then call
mysql_thread_id() again to see
whether the identifier has changed.
If reconnect occurs, some characteristics of the connection will have been reset. For details about these characteristics, see Chapter 20, C API Automatic Reconnection Control.
Zero if the connection to the server is active. Nonzero if an error occurred. A nonzero return does not indicate whether the MySQL server itself is down; the connection might be broken for other reasons such as network problems.