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Introduction

Due to the nature of these community clients being separated from Steam’s infrastructure, you can’t add friends through Steam and join their games directly. The connection method depends on which game you’re playing:
  • CB Launcher friends (easiest): BOIII, IW6x, S1x, H1-Mod, and IW7-Mod can invite and join friends from the launcher itself. This is the recommended method and has its own guide: Play with Friends Using CB Launcher.
  • Discord or a match token: the same five clients, for players running the client directly instead of through the launcher. Jump to this method.
  • Built-in friends system: Plutonium clients (T4, IW5, T5, T6) use their own in-game friends list. Jump to this method.
  • Radmin VPN or port forwarding: Every other client, and a fallback for the clients above if a direct connection can’t be established. Jump to this method.
  • External guides: Modern Warfare 2 SP/Spec Ops (IW4-SP), Modern Warfare 3 SP/Spec Ops (IW5-Mod), and Black Ops 4 (Project BO4) each have their own external guide. Jump to this method.
The following clients support joining and inviting friends from the launcher, with no IPs, console commands, or extra software: Link your Discord account once and the launcher’s Friends page lists your Discord friends, shows what they’re playing, and gives you Join, Ask to Join and Invite buttons. It starts the right game in the right mode and connects you automatically, and the host doesn’t have to open their match first.

Play with Friends Using CB Launcher

Linking Discord, hosting, joining, inviting, and troubleshooting
Use the launcher’s buttons rather than Discord’s own invite and join buttons. Discord limits how fast invites and join requests can be sent, and accepting in Discord while the host’s private match is still closed costs an extra approval round trip. The launcher avoids both.

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Playing Without the Launcher

Use this only if you run the client directly instead of through the CB Servers Launcher, or you haven’t linked your Discord account to it. It covers the same five clients as above. Connections are still made automatically through NAT hole punching — no Radmin, Hamachi, or port forwarding required.

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Hosting a Match

1

Start a private match

Launch the client and start a private match as you normally would.
2

Open to Friends

Open the pause menu and click Open to Friends. Your Discord status updates to show a joinable game.
Don’t see the button? Some custom maps and mods (especially on BOIII) override the in-game menus. Open the console (~) and run nat_host instead — it does the exact same thing.
3

Invite friends

Click the file attachment (+) button in a friend’s DM or any text channel to send an invite. Friends can also join directly from your Discord status without an invite.
Make sure Discord is running and Activity Status is enabled so your game shows up.
4

Close match

Want to close the match after a friend joins? Open the pause menu and click Close to Friends (or run nat_host again in the console).

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Joining a Friend

Launch the game in the same mode as the host before joining — for example, join in Zombies if they’re hosting a Zombies match.
Click Join on your friend’s Discord status, or accept their invite. You’ll connect automatically — no IP or console commands needed.
This works when the host is on a normal home internet connection. Restrictive networks such as mobile hotspots, hotel, or public Wi-Fi can block the connection. If you can’t connect, use Radmin VPN or port forwarding instead.

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Games with Built-in Friends

Some clients handle private matches through their own friends system rather than direct IP connections. First add each other to your friend list, then use the per-game guide below to join a friend’s custom game.

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External Guides

Some clients handle private matches differently enough that they’re best covered by their own external guide:

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Radmin VPN or Port Forwarding

This is the only method for IW4x and HMW, and the fallback for BOIII, IW6x, S1x, H1-Mod, and IW7-Mod when neither the launcher nor the Discord method can connect you.

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Client Port Numbers

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Method 1: Hosting with Radmin VPN

This is the easier method and doesn’t require router configuration.

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Additional Prerequisites

  • Radmin VPN installed on all players’ computers

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Initial Setup (All Players)

1

Install Radmin VPN

Download and install Radmin VPN.
Steps 2 & 3 may not be necessary if you already allowed the client through Windows Firewall when you first launched it.
2

Allow client through Windows Firewall

  1. Go to Windows Firewall settings
  2. Click Change Settings > Allow another app
  3. Browse to your client executable
  4. Ensure all boxes are ticked, then click OK
Video guide for firewall settings
3

Create firewall rules for your client port

  1. Open Windows Firewall with Advanced Security
  2. Create both Inbound and Outbound rules for your client’s port (see port numbers above)
  3. Important: Set protocol to UDP, not TCP
Video guide for firewall rules

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Network Setup (Host)

1

Create a Radmin VPN network

  1. Open Radmin VPN
  2. Click Network > Create Network
  3. Set a network name and password
2

Share credentials

Give the network name and password to your friends.

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Network Setup (Friends)

1

Join the network

  1. Open Radmin VPN
  2. Click Network > Join Network
  3. Enter the network name and password provided by the host
  4. Click Join

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Starting the Match (Host)

1

Start a match

  1. Launch the client via the CB Launcher, or open the client executable directly (e.g., boiii.exe)
  2. Navigate to your desired mode, choose a map and start the match
2

Find your Radmin IP

  1. Open Radmin VPN
  2. Your IP will be displayed in the network list (e.g., 26.118.191.42)
  3. Share this IP with your friends
Radmin VPN IP
3

Limit player count (optional)

  1. Open the console (` or ~ key, under ESC)
  2. Type: com_maxclients X or sv_maxclients X (replace X with desired player count)
  3. Example: com_maxclients 2 for 2 players total

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Joining the Match (Friends)

1

Wait for host

Wait for the host to be IN the actual game/match, NOT in the lobby.
2

Connect via console

  1. Open the in-game console (` or ~ key)
    • On 60% keyboards: Fn+ESC
  2. Type: connect RadminIP:PORT
  3. Example: connect 26.118.191.42:27017
  4. Use the Radmin IP provided by the host and the appropriate port for your client
3

Play

Wait for the game to load and have fun!

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Need Help?

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