I have the same issue, as do my friends. I have also attempted forwarding ports 2302-2305, 8766, and 27016 as well as setting up an echo ping response within Windows firewall but none of that has helped. When they try to connect via steam it says "No connection", and they can't host games either, it does the same thing.
May 10 2016
I think we might need to summarize all of the information about the issue in the new parent ticket, as it says it's awaiting more information or something like that.
Shotgun, note that Fireball can't really do anything more than reopen the ticket for us, he's a moderator, not a community manager like Iceman. That being said thank you Fireball for helping and at least reopening the ticket for us. Now we just need Iceman to actually look at this again, try to get it fixed, and hopefully keep eyes on it to ensure it gets fixed...
It's also extremely frustrating waiting 10+ days between responses. I mean I know the community managers and moderators probably have their hands full, but this issue is quite a bit more serious than feature suggestions and other small bugs. I would normally play anywhere between 20 and 100 hours of ArmA in a month, and I've probably played less than 7 in the past 2 months due to this issue. I even had a friend buy the game during the summer sale and he hasn't even played it because we can't play together. This issue needs more attention.
Perfect summary of the issue Rimp. This process is going far too slowly for such a game-breaking issue. I feel like Iceman thought the problem was fixed and moved on, and Fireball's responses are a little confusing and he hasn't responded in 9 days. This issue has to be affecting a lot of people seeing as how it's also affecting the friends of everyone in this thread. A game breaking issue like this needs to be addressed quicker and more seriously. I say at this point we start a new ticket with all the information we've gathered together here and all vote it up quickly to get their attention.
On dev build, issue still persist for my friends and I. I have my ports forwarded, and now instead of them not having connection to the server they're stuck in the loading screen while trying to join. We should probably start a new ticket seeing as how Iceman hasn't responded in over a week and the issue is very much game-breaking for quite a few people.
Have been having this issue since the last patch as well. Tried forwarding steam ports, tried disabling firewall, tried setting up echo ping response, nothing has worked. Happens with all of my friends as well, none of us can host a server.