Below is an example using the "ServerisOnline" function. If you prefer to see 'Online' or 'Offline' instead of 1 for online and 0 for offline, you can add 2 more string parameters and do some comparisons to display a message showing I/O Status.
You can copy the cicode below to your project and rename the IOservers to your IOserver names.

FUNCTIONIOServerConnected()

INT itemp1,itemp2;

//Checks if the standby IOServer is online in this example the standby IO server is "IOServerS" if itemp = 1 then it is online
itemp1 =ServerIsOnline("IOServerS","Cluster1");
Message("Standby IO",itemp1,0);

//Checks if the Primary IOServer is online in this example the primary IO server is "IOServerP" if itemp = 1 then it is online
itemp2 =ServerIsOnline("IOServerP","Cluster1");
Message("Primary IO",itemp2,0);

END