Hi, hope someone with experience in HC setup can help you, as I know almost nothing.

Yes you have to have the ip or ip-range configured in your server.cfg file...

example for local ip's:

localClient[]={127.0.0.1, 192.168.1.10, 192.168.1.210};
headlessClients[]={"127.0.0.1","192.168.1.10","192.168.1.210"};
battleyeLicense=1;

see more info:
https://community.bistudio.com/wiki/Arma_3_Dedicated_Server#Headless_Client

@mike187 Cheers, but where is server.cfg? I can't find it anywhere on my computer. I have the workshop version of this which I feel may make it harder. I've exhausted all my googlefu trying to find it too.

its the server config file of your friend on his server where he sets the password and the admin password for his server. He must add your IP to his config file so you will be able to provide the HC.
I only tested this HC with my local Server... I'm not sure what your friends server specs are but he could try to run an HC from the same machine if he has enough CPU/ram power to run it.

Send that link above to your friend with the server and there is everything explained what he needs.

He's just hosting locally though the ingame system, and can't find a server.cfg anywhere. Does he need to host a dedicated server or something? Basically the idea is that I can take some of the load off him since his RAM is struggling, and usually it's just the two of us.

Originally posted by Kikkawa Hiroie:

He's just hosting locally though the ingame system, and can't find a server.cfg anywhere. Does he need to host a dedicated server or something? Basically the idea is that I can take some of the load off him since his RAM is struggling, and usually it's just the two of us.

First of all l would highly recomand reading through the Wiki Mike187 posted and set up a dedicated server because l beleive he is right and you do need a config file for the HC IP's though you might able to host a dedicated server using the game files on steam instead of using steamcmd but that is something your friend and you will have to try and figure out which shouldn't be to difficult just time consuming.

A few things to note

*Only admins can see if headless clients are connected

*Don't run it though a bat file instead create a shortcut for arma3server.exe and put your command into the target box as shown here http://imgur.com/nNRiH9x

*I noticed that your target line is wrong so here is mine l use to connect to my local server with a headless client and as you can see after -connet and -password l have an = sign rather you have an - and l also notice you don't have -name=headlessclient which l think is required.

"D:\SteamLibrary\SteamApps\common\Arma 3\arma3server.exe" -client -connect=(P -name=headlessclient -password=0000

*Fixed version of yours

E:\Games\Steam\steamapps\common\Arma 3\arma3server.exe" -client -connect=(IP) -port=230-name=headlessclient -password=(his password) -mod-@CBA_A3; @ace; @RHSAFRF;

Originally posted by Kikkawa Hiroie:

He's just hosting locally though the ingame system, and can't find a server.cfg anywhere. Does he need to host a dedicated server or something? Basically the idea is that I can take some of the load off him since his RAM is struggling, and usually it's just the two of us.

Headless client is only achievable for dedicated servers and it won't lower his RAM usage. Headless target is to offload the AI management to provide a dedicated AI computing hence more iterations for better behavior. The dedicated server will then concentrate on the environnements, scripts and anything, so it will use the same ressources, but the AI will not be part of its calculations.

If you have set up a dedicated, as dadey60 recommended it, you should use the shortcut arguments instead of the command line, less typos risks until your mod list is reasonnable : parameters field is limited in text lenght.

The following is confirmed working:
"[PATH_TO]\arma3server.exe" -client -connect=[IP] -password=[PWD] -nosound -port=[PORT] -name=[NAME] "-mod=[@MOD]"

[IP] : Server target IP
[PORT] : Server target Port
[PWD] : Server password if required, else remove the parameter
[NAME] : random name to have the profile created
[@MOD] : any additional mod you'd like

You have to be carefull of the typo : any parameter is followed by '=' before the argument and not '-' like in your post. Also, you could have spaces in your mod names, so you need to add quotes on the section : "-mod=@mymod1;@my mod2;@my_mod3"
Do not add spaces after the semi-colons.

Once your shorcut is done, check in your server config that the Headless IP is registered. If you choose to use TADST its simple, you just have to refer your IPs in the main page under the headless section. If you have multiple HCs, IPs have to be seperated by a coma :
http://i.imgur.com/0wvoUCW.png

If you don't use TADST, you will have to manually add the lines in the server.cfg
To locate the file used by your server you can check the parameters in command line used to launch it. It should look like : "-config=[PATH]\server_config.cfg" (.cfg file name can be different, you should refer to the tutorials to setup a proper dedicated server).
Once you have the file, just add the following lines with your IP :
The use of the localclient command should be limited to headless clients localized within the server LAN or hosted on the same computer than the server.
So considering your statement, you will only need the following :

Then you launch your server, and start the headless client. It should try to connect to the server. The console is not very chatty, but you should be able to see if you have errors in the password and/or mod list.
If you manage to connect it, remember that only the server admin can see the headless client in the mission lobby.

A headless client cannot be managed inside a mission, if its connected it will automatically use an available virtual slot. If the mission is not headless-ready, the headless will just stay idle and consume a player slot nonetheless.