How to check for server availability? [v9.3.1, Linux]

Hi all.
I'd need to check from a C language program whether the server is
running or not.
I was planning to use either "PGPing PQping(const char *conninfo)" or
"ConnStatusType PQstatus(const PGconn *conn)".
I have my program running and checking from time to time whether the
connection is kicking and alive.
In order to test the things I've done the following: while the program
is waiting for input I simply restart the postgresql server.
The issue is thayt both functions return PQPING_OK and CONNECTION_OK
respectively.
When I forward the request, I get an error: "FATAL:  terminating
connection due to administrator command".
How can I reliably check the server status?
TIA: