I hope there is a vine like this out there, I'd like to have one too, but I don't know of a constant fragrant bloomer...

You might be happiest by using several different vines since any particular one is unlikely to bloom all season. Like Clematis for earlier blooms, coral vine for blooms later, maybe a rose for mid-summer if it can be placed where people won't get poked. Beware of thuggish vines that could tear up your porch, like wisteria or trumpet vine (which only bloom for short periods anyway.) Of course there's jasmine but I don't know that vine well enough to gauge its' suitability for a porch post. I've seen some pretty big, unruly ones. You may also like some hanging pots to help decorate your porch.

I was envisioning a similar project here this year and think I'll stick to vines that die back to the ground for winter, or don't mind being trimmed that much occasionally because the porch needs to be painted periodically, something that might be a consideration for you also. I've put it off so far because it's tricky with the way the water flows off of the porch roof - right on the spot where one would want to put a root ball of a vine to grow up the posts. Not sure it's possible to plant that area without having a washout the next time it rains really hard. Probably would need to place some rocks and/or a sturdy border.

If you could show a pic, that always helps to get more specific suggestions.

i would plant something that is more of an annual vine for constant flowers during the growing seasons. vines like mandevilla, alamanda, thunbergia grandiflora(sky flower) or thunbergia alata (black-eyed susan vine) are tropical and can either be replaced each spring or you could grow them in containers, letting them sprawl over your railing and take them into cool storage during winter.
the site that you have should be suitable for these. you could also plant something like morning glories or moonflowers at the base to climb and mingle with them and add other colors. the white moonflowers open in late afternoon, normally from about 4:00pm until the next morning and are very fragrant while the morning glories would give you flowers from sunrise though mid-day.

Have you considered crossvine? It isn't really very fragrant, but has dark green leaves in summer and the leaves turn purple in winter for year-round interest. Blooms in spring anywhere from pale orange to red depending on the variety; most have yellow throats on the blooms.

There are ornamental varieties available, but it grows natively in woodland edges, so you could transplant one you prefer. And it's one tough plant. It grows fast and gets big but it's not a bully like trumpetvine.

I agree that if you want year-round blooms, a mixture of vines might be the best approach.

Thank you all for your suggestions. I've never considered a Cross Vine, I'll do some research on that one. Hopefully it will be lovely for the Spring and Summer seasons!