The following is intended to serve new, as well as, returning players as a reference to solve the most common problems and questions. (taken from freshmeat-blog.de.tl)

TECHNICAL QUESTIONS

I installed Diablo for the fist time. Unfortunately I can’t connect to Battle.net. The following error message gets displayed: "Unable to connect to the Battle.net. If you are using a modem to connect to your service provider and are not configured for Dialup Networking, you may have to initiate the connection manually."
-Make sure to run the newly released "GOG Diablo" version. The old classic version is not supported by Battle.net anymore.
-You can however still use the “Classic Diablo” version to play via one of the many VPN applications (e.g. Hamachi & GameRanger). Both versions are compatible with each other. Make sure to patch "Classic Diablo" to version 1.09.

I can’t seem to find any games on Battle.net. Is activity really so bad these days?
-The reason for you not seeing many games in the "Matching Public Games" list is, that only games within your level range will get displayed there. The overview below shows what ranges of character levels will be matched together: 1 | 2-3 | 4-6 | 6-9 | 10-14 | 15-19 | 20-24 | 30-34 | 35-39 | 40-44 | 45-50
-If you want see a complete list of available games, it’s possible to query one of the many channel bots with the "!games" command. The bot will list all active games, as well as detailed information about the creator(s).

I can’t join most games on Battle.net. I always receive the following error message: "You were unable to join. The game you have selected is not responding. The latency to the game creator is too high."
-This problem usually occurs because the host of the regarding game session has not forwarded the needed ports for Diablo on his router and/or Firewall. Usually there is no way to join these games at all. Talk with the host and indicate him to setup the ports as described below.

Other players can’t join my created games on Battle.net. They always receive the following error message: "You were unable to join. The game you have selected is not responding. The latency to the game creator is too high." How can I fix this problem?
-Don’t worry there is a solution for this annoying problem. All you have to do is to setup your routers ports permission the following way: 6112-6119 TCP & UDP out & in
-Occasionally, it’s necessary to create an exception for Diablo on your Firewall as well.
-A detailed guide how to forward your ports on many different router systems can be looked up here.

Diablo tends to crash without any replicable reason while I’m playing. The following error message "Storm Error" gets displayed. What’s the reason for it? How can I prevent it?
(Note: This problem might be fixed in the GOG Version)
-This problem occurs mainly to people with multi-core processors. You can fix it by forcing Diablo to run on only one single processor core. Just follow the description below:
-When Diablo is running press "ctrl-alt-delete"
-Go to “Task-Manager”
-Then go to “Process”
-Right click on “Diablo.exe”
-Now click on “Set Affinity”
-Disable all checkboxes except one.
-This should fix the problem entirely. However, you unfortunately have to redo these steps every time you start Diablo.

Colours, icons and the chat in Diablo are displayed wrong/faulty. Everything looks like being drawn on acid. What's going on?
(Note: This problem might be fixed in the GOG Version)
-This so called "Rainbow-colour bug" occurs mainly, if you run Diablo on modern operating systems. You can download Blizzards official fix for this problem right here. Make sure to pick the correct version for your operating system (32 or 64 bit).
-For all other compatibility problems with the old “Classic Diablo” version, take a look into our "Diablo Compatibility Guide".

I'm unable to whisper to other users with the default /w, /msg and /whisper commands. The following error message gets displayed: "You can‘t whisper that user." Is it still possible to send private messages to other users?
-The classic whisper commands unfortunately don't work for Diablo anymore. You can still whisper to other users though. You have to add them to your friends list with the /f add nickname command, and use the /f msg or /f m command to send messages. Admittedly this is not the best way to send "private" messages, as you whisper to every player on your friends list with these commands. In case you should need privacy, you have to remove unbidden ears from your friends list with the /f remove nickname command.
-An extensive list of Battle.net commands can be looked up here.

Where can I find my Diablo singleplayer savegames and/or multiplayer characters?
-From version 1.08 onwards, savegames, as well as character saves, are stored in your Diablo directory. Multi_x.sv files represent your multiplayer characters, and single_X.sv files your singleplayer savegames.
-Earlier game versions store savegames and character saves in the Windows folder.

My Diablo CD tends to cause very long loading times ingame. Sometimes I even experience lag. For example when I change my gear. What can I do to get rid of this problem?
(Note: Fixed in the GOG Version)
-I recommend to create an image file of your CD. This can be done by pretty much all CD/DVD recording applications. You can use this image file as a replacement for your CD. Loading times will get decreased to a minimum. Consequently, the well known "loading lags" won’t occur anymore.
-To load/mount an image file, it will be necessary to install a program which is capable of creating a ‘virtual CD/DVD drive’. I recommend "DAEMON Tools Lite". It’s small and very user-friendly.

GAME RELATED QUESTIONS

My character appears to have lost Health Points and/or Mana Points permanently. What’s the reason for this?
-Health Points can get decreased permanently by a Zombie named "BlackDeath". These creatures can only occur on dungeon level 3 to 5. They are coloured in a bright yellow, which makes identifying them quite easy. With each hit, they will decrease your characters maximum health permanently by 1 point!
-Maximum Mana can be decreased by 3 shrines: "Fascinating Shrine", "Ornate Shrine" and "Sacred Shrine". Each of them decreases your mana pool permanently by 10%! Consequently, it’s advisable to stay away from "Cauldrons" and "Goat Shrines" as well, since they can trigger any shrine effect randomly.
-A complete shrines list can be looked up here.

What are the differences between singleplayer and multiplayer mode?
-Diablo characters can be created as single or multiplayer characters. This decision must be made at the time of character creation, and it can not be undone or changed later on. Aside from the obvious fact that you must make a multiplayer character to play with friends (over a LAN, TCP/IP, or Battle.net) there are a few major differences between SP and MP.
-Difficulty: Multiplayer is much harder than singleplayer. The monsters have roughly double the hit points (even on Normal difficulty).
-Quests: Only 4 of the 16 quests are found in multiplayer, and these 4 are found in every game.
The quests are simplified as well.The special sub-levels for the Skeleton King and Lazarus are not found in multiplayer.
-Uniques: All unique items given as quest rewards are not found in multiplayer.
-Elixirs: Pepin the Healer sells strength, dexterity, and magic elixirs to any single player character over level 25. He never sells elixirs in multiplayer. Adria the Witch sells strength, dexterity, and magic elixirs in single player and multiplayer, but infrequently and randomly.
-Experience per kill is capped in multiplayer. Monsters are never worth more than 200 experience per player level, with a maximum of 10,000 at level 50. They can be worth over 100,000 each in single player on Hell difficulty, making leveling up past level 25 much faster in singleplayer.

My character walks awfully slow. Is there anything I can do about it?
-In classic Diablo there is no way to make your character walk any faster. In Blizzard’s official expansion "Diablo Hellfire", there is an option to let your character run. This however only works in town.
-An alternative way to enhance the movement speed of your character is to learn the "Teleport" spell. With a solid mana pool, characters can move through an entire dungeon level in a couple of seconds.

Is there a way to access higher difficulties in singleplayer mode?
-Yes there is a way to enable "Nightmare" as well as "Hell" difficulty in singleplayer. All you have to do is to start a multiplayer game on "Nightmare" or "Hell" difficulty. Then simply quit back to the main menu and start a singleplayer game. The singleplayer game will be the same difficulty as the multiplayer one, including the value of experience per monster, gold drops, etc.

Is there a way to skip the end movie?
-All you have to do to skip Diablo’s end title, is to minimize the game window. Simply press "Alt+Tab" , the "Windows key" or "Ctrl+Alt+Del" to force this effect. Now when you return back to the game, you will find yourself either in your local channel, or in the main menu.

Is there a way to obtain Diablo’s drops?
-Yes you can obtain his drops by simply going up to town while Diablo gets killed by another player. The players in town won’t get dropped out of the game by the ending title.

What’s the best way to exchange gear between my characters?
-The most common (and legit) way to do this would be to ask another player to host a so called "mule game". Alternatively, there are quite a few third-party solutions for this issue. One would be "Diablo Torch", or alternatively "Ulmo's Stash". Both implement an ingame stash functionality to Diablo. Another solution would be "Blue Scorpios Diablo Saver". With this app, you can export items (only your own!) as well as characters to your hard drive, and load them into the game when desired. You can find detailed information about these applications in our "Technical Support" section.

What about the Cow level? Is this level really existing in Diablo?
-No the "Cow level" is just a myth which was invented in the early days of Diablo. The main purpose of this myth was to fool around with new players. A few of the methods to access the "Cow level" involve very tedious tasks. A classic one would be to click on one of the cows in town a couple of hundred times ;-)
-It’s worth to note, that Blizzard actually implemented a "Cow level" in Diablo 2.

How to achieve maxed spell levels on Rogues and Warriors?
-All you have to do is to run for "Enchanted Shrines",until all spells are maxed out except the ones which are readable even without having a very high magic attribute. The spells with the lowest magic requirement from s.lvl 14 to s.lvl 15 are: "Fire Bolt" (177), "Heal Other" (192) and "Healing" (192).

What does the term "legit" stand for?
-"Legit / Legitimate" basically means to play the game the way it is intended to be played. No cheats, no hacks, no exploits, no dupes, no game breaking third-party programs.

What's a good Discord channel to get in touch with other Diablo Players?
https://discord.gg/bfZK4uz

Any Diablo related websites you can recommend?
http://freshmeat-blog.de.tl
http://diablo2.diablowiki.net/Diablo_I
http://realmsbeyond.net/diablo
http://diablo-evolution.net
http://www.bigd-online.com/JG/JGFrame.html

I doubt this error will ever come up, as they have disabled the ability to create/join games without port forwarding.

First of all big thx for all this , its really nice info :D
Can u please name me a active channel with a bot, its look really usefull i wanna try that thx alot

I see it all the time. I did not have to portforward to create or join games, but there would be the 6112 red message entering Bnet the first time, which is gone the second time entering Bnet.

Before I portforwarded, I could create games but I guess nobody could join mine. After portfwarding, it still depends on your connection (usually 3 bars red-yellow for mine, never green because I think I am behind ISP NAT and don't have public IP), but some managed to join my created game finally.

Yeah this whole thing where people get the message once, then leave, then they don't get the message again is pretty weird in itself.

The thing is, people who get the 6112 red message cannot create or join games, because the Create and Join buttons are greyed out, you can't click them. I only found one single topic mentioning this issue, and no solution to it. So if you remove your port forwarding now and connect to battle net, you don't have the buttons greyed out?

Yeah that was what happend to me.

As mentioned I did not have to portforward to bypass the 6112 message and able to create and join games (not greyed out), Windows Firewall though does need to allow Diablo.exe for public/private/domain, allow edge traversal and allow any ports. And maybe you have other firewall programs blocking it.

Port forwarding only helps others join your hosted game. Before I portforwarded, no one ever joined (I guess they see the high latency error). But after I forwarded ports in the router, 2 players were able to join my game one night. Note that if I went to whatismyip and check if my 6112-6119 is open, it still says closed because I am behind ISP NAT or firewall.

here's a guide for portforwarding and firewall: https://www.tapatalk.com/groups/freshmeatbutchery/portforwarding-guide-old-tristram-forums-t10.html

people can't join each others games in nightmare or hell without 3rd party hack files, should be in the faq

Just added it.

thanks

i had downloaded torch but had forgot to try it. did you get it to work on gog?

i tried the win 10 and the latest beta one and neither worked for me.

Yes Torch works with the GOG version. Start the game, tab out run InjectorConsole.exe and then execute Inject.bat. Both with administrator privileges.

thanks, had tried doing bat with admin but not the injector, windows 10 worked but not the beta version

вернуть потом как то можно?

получается, что можно качаться до высокого уровня, но остаться без здоровья навсегда?

I recommend against Daemon Tools Lite. It used to be good and fast, but then it turned into bloated adware for the non-Lite version.

Instead, go for Virtual CloneDrive. It's fast, small and doesn't contain any ads or promotions.

DT Lite indeed to adware this time. Same as Alcohol 120%. But if you want ome alternative - make sure they work with SPTD driver. Only that virtual drives program exactly irtual drive, and not virtual catalog program. It absolutely different things. CD disk image work properly (including installation) only in virtual SCSI or IDE drives. Native Alcohol and DT drives can handle with installation(always?), but not DRM emulation. I do not know other program that can handle with installation properly. Even if INSTALLERS say that intalation complete - do not believed it. Some files missed, and some other files can be named wrong (lower\upper letter).
It just like if you download ISO and extract it as archive without installation - that program allow do that with some other formats (like 7zip for 7z or WinAce for .ace, etc). Always use only canonical Daemon Tools (Lite) and Alcohol (120% FE) and SCSI \ IDE drives. Still no (no one) alternatives for them.

As i can see, Virtual CloneDrive is a wrong program for that. And devs same as other lied about "100% like hard CD-rom driver".
I guarantee, this program work just as WinMount. Do not trust to My Computer drive icon. DT Ultra can mount image to catalog or catalog to virtual drive. It not a CD image mounted in a virtual driver. All other program - it not a image mounted in virtual driver.