properly take -f flag as an argument.
hide local variable.
implement macro version of htons().
hold a TCP port number in network byte order.
more verbosity.
set errno at lower level functions, and propagate errno to upper level
functions.
fix wrong pair of min/max values.
change errno in order to tell no search results from invalid keywords error.
add a useful function to handle struct sockaddrs.
implement network related code more.