Why must crafting machine fluidboxes be input or output types?

[Pid]

"Failed to load mods: Error while loading entity prototype "forestry" (assembling-machine): Crafting machine fluidboxes must be input or output types." Why? What is the benefit of this restriction? What is the best work around?

[eugenekay]

Crafting machines are meant to craft a Recipe. Input fluid boxes provide supply for a Fluid Ingredient. Output fluid boxes hold the Fluid Product of the recipe. You need to have the boxes at different locations in order to be able to handle recipes with both a Fluid Ingredient and Output.

What other use could you possibly have!?

[Pid]

I thought it was about whether an input fluid can go from one machine to another through the connections. I think I have it figured out now. Thanks.

[eugenekay]

For "Passthrough" style fluid connections take a look at the electromagnetic plant prototype. It uses "input" and "output" fluid boxes defined separately; but there is additionally a FluidFlowDirection specified as "input-output" to permit sharing of that fluid with neighbor machines. Note that the connections are still specified in two different X/Y locations so there is no conflict if a recipe has both a Fluid Ingredient and Output.

Good Luck!