A turf war is erupting in the residential real estate industry, with the biggest names — including Compass, Redfin, Zillow and Homes.com — falling into two increasingly stratified camps when it comes to so-called “pocket listings.”

Such listings are houses for sale that are shown privately to select groups before going to the general public.

Brokerages and real estate portals on one side believe the private listings are beneficial because they offer sellers privacy and control, as well as a chance to test the waters on aspects of a home sale like staging and price. Those on the other side believe they make the market less fair, and can also drive down sale prices by reducing competition.

All brokerages agree that listings are precious currency. There are more real estate agents in the United States than there are houses for sale, and the more listings an agent can show to a potential buyer, the more likelihood they have of closing a deal and collecting a commission.

On Friday, Compass sued a Seattle-based listing database in federal court, accusing it of “monopolistic” and “anticompetitive” behavior that it says has damaged both Compass’s reputation and business.

The database, Northwest Multiple Listing Service, refused earlier this month to allow any of its listings in the Seattle region from appearing on the Compass.com website. Northwest MLS reversed its stance a day later, but continues to enforce a rule that requires brokerages to enter home listings on the MLS immediately, or not at all.