I live within in about five miles from the Seabee base in Gulfport. They do have an RV park on base. I just looked it up on-line and here are the rules:
The Shields RV Park is Recreational Lodging open to all Active Duty, Reservists (both Active and Retired), Dependents, Retirees, and DoD Civilians
Accommodations: Shield’s RV Park offers 68 sites. Amenities include free Cable TV, Wi-Fi, Water, Sewer, Electric, Shower Facility, On-site Coin Operated Laundry Facility, Mail Service, telephone hook ups, a dump station, and 20, 30, 50 amp services. There are 53 pull through sites and 15 back in sites. Shields RV park has ADA restrooms and shower facilities (one for each gender). There are 7 sites for short term stay only. Five of these are back-ins and four are pull-through. These pads are available for customers wishing to stay 14 days or less. There are also four overflow sites available at the park entrance for overnight stays (dry camping only).
RV Park Prices
$10/Nightly (Dry Camping)