MAXSOC parameter
The SELECTEX call must test each bit in each string before returning results. For efficiency, the MAXSOC parameter can be used to specify the largest socket descriptor number that needs to be tested for any event type. The SELECTEX call tests only bits that are in the range 0 through the MAXSOC value minus 1.
Example: If MAXSOC is set to 50, the range is 0 - 49.