is it possible to connect 4 Hoppers ?

The cheapest way is one DPP44 and one DPP33 on the DPP44's passthrough ports. 1st port on the DPP44 takes the power inserter, then the remaining three go to a duo node, and the 3 on the DPP33 go to the second duo node. Connect client ports together and voila. Everybody sees each other. ;)

Do you mean a DP34? I have one of those, and it has passthrough ports going to my DPP33. I have no idea why they left off the passthrough ports on the DPP33.

Last time I priced them a DPP44 was nearly twice the price of a DPP33.
Oops, Yes I meant DP34. I have a couple of them here no longer in use.

Just checked again at Dish Depot and the price for the DPP44 is just $10 more than the DPP33. It used to be a lot more. I paid 99 for mine some time back, now it is 59.
 
Tx Brian,
I have 4 Hoppers and 8 Joeys.......what is the best way to connect all this ??M.
Best way is to use the thumbnail from reply #6 on page one of this list and then add Joeys to the remaining client ports using splitters.
I don't know how far you can go with splitters, someone else here will have to answer that.