TCP select flag byte for TCP select conditions. It is mapped as follows: -bit(1) = ON if active open, off passive -bit(2) = ON means timestamp option supported -bit(3) = ON when select for read issued -bit(4) = ON when select for write -bit(5) = ON when select for exception -bit(6) = ON means this is controlling -bit(7) = ON if accept in progress -bit(8) = ON means we are at OOB mark