/* Assures that the config option is either a service name (a string) or a port
* number (an integer in the appropriate range) and returns a newly allocated
* string. If ret_string points to a non-NULL pointer, it is freed before
* assigning a new value. */
/* Assures that the config option is either a service name (a string) or a port
* number (an integer in the appropriate range) and returns a newly allocated
* string. If ret_string points to a non-NULL pointer, it is freed before
* assigning a new value. */