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 Section 3.6.8, “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.