Hellfire does not have official MP support, when enabled via hacks you will end up with .drv files that are encrypted to your computer name can can there for not easily be moved to a different system.
There are also some comparability issues with the item formats.

That being said it has been done a few times before. I would suggest going to the DevilutionX chat and ask if someone there can help you, be sure to provide the name of your computer so that the file can be correctly decrypted.

Thanks, what is devilution chat ? discord, or github, or on diablo ?
I found a program, bobafett, that can save character in .CHA file to move them in single player that can be moved to devilution, but the question is, can we convert SP to MP on devilution after ?

discord

no SP and MP items have different values and cannot be converted

Hi, i've just teste on diablo (I'm not on my pc with hellfire) and with bobafett we can export MP to SP, so i supose the method to convert item from MP <-> SP is known and working. I even found convert program to diablo .ITM <-> hellfire .HIF.

they are for sure going to have morph issues with the items

WHat is a morph issue ?
ITem look like the same.
IS there a item you'd like to test that i coul'd post screenshoot in SP and in MP, or maybe the .itm file if you'd like to see how it is done ?
MAybe bobafett is working because it need to be in game, so it can make the change only by appliing "pure" item stat independently if the game is in SP OR MP ?

The items would appear wrong to other players and also to you if you cause them to be interpreted over the network or start a new game.

Most trainers work by injecting the generated item in to active memory and not the actual data format.

OK, tested with some .itm bank found on the net.
Look like cheated item regain their base stat or form after relogin to a new game.
Look like legit items remains the same, even whith save ".sv" transfered to devilutionX
LOOk like some item glitch when ".sv" is changed to ".hsv" to import them directly to devilutionX hellfire

Diablo has two ways of storing items. One is very compact, is used in save games, and is sent over the network. It is too compact to be usable during play, because it is just a description of how the item was generated (town/monster, level of origin, a few other things). The other is a fully expanded representation with all the statistics computed. Cheat programs often import/export the expanded form, which means the item can have impossible statistics. However, once it is compacted down for save, and then re-expanded on load, it returns to its original properties.

As a complication, since Hellfire allows item affixes that Diablo does not, attempting to expand an item generated in Diablo in a game using Hellfire data (or vice versa) may not produce the same item as originally generated. This is usually referred to as "morphing." This is why your legitimate items survived import into Diablo: they were regenerated to the same values they already had. The cheated items did not survive: they were reset to the legitimate item from which they were originally created. The items imported into Hellfire did not survive: they morphed into what you would have gotten from the corresponding drop/purchase circumstances in Hellfire.

OK
So SP and MP have different value for the items, but if passed throught bobafett converted ito a .itm, when quitting en relaunching the game the item is automaticaly converted to the value it would have if the game is in SP or MP ?

Maybe saying something idiot, i'm not competant, but if the STAsh from deilutionX was storing items in the .itm format we could access to all item independently if the game is in SP or MP and the game could change these values once the item is on a SP character or MP character ?

it uses that format, but the compacted format is used for multiplayer communication. You will have different items show up between players if you did so.

There is no way to convert them as they are just seeds for the RNG engine. You would have to search through possibly millions of items to find one that is identical in the other game, and you might never actually find one.

OK so i've installer devilution on another PC to test on multiplayer game and taken screenshoot (say me if i did something wrong) :
Step
1 create new char in SP diablo 1.09
2 Buy a magic buckler
3 export into .itm file (bobafett)
4 import on a new MP CHAR
5 copie first MP on devilution
5 create multiplayer game joined by another new MP char on second PC
6 give the bucler to the second char
7 quit and relod second char with the buckler

The buckler remain the same, or maybe i misunderstood what is morphing and it morph in another way ?

for screen attach

screen

I'm not sure what you are asking or saying.

Sorry my english is so bad :s
I've taken a buckler from a SP char and transfered it on a MP char and tested if it morph.
It remain the same even if i give it to another player.