So you're trying to play Minecraft with friends on your local network using version 1.21.5 and hit a wall with port settings? Been there. Last weekend I spent two hours troubleshooting why my brother couldn't join my world before realizing Windows Firewall was silently blocking everything. Frustrating as heck, but we finally got it working.

Why Ports Matter in Minecraft LAN Connections

Okay let's cut through the tech jargon. Think of ports like apartment numbers in a building. Your router's IP address is the building address, and ports are specific doors for different services. By default, Minecraft uses port 25565 - but when you specify a custom port like in 1.21.5, it's like telling your friends to use the back entrance instead of the front door.

The moment you hit "Open to LAN" in Minecraft 1.21.5, the game actually shows this message in chat: Local game hosted on port XXXXX. That XXXXX is your golden ticket. Ignore that number and you'll be stuck staring at "Connection timed out" errors like I did last month.

Essential Requirements Checklist

• All computers running identical Minecraft versions (1.21.5 exactly)
• Devices connected to same local network (WiFi or Ethernet)
• Host computer's local IP address (more on finding this later)
• Specific port number used when opening the world
• Firewall exceptions added for Java and Minecraft

Step-by-Step: Connecting Using Port in 1.21.5

Hosting the World (The Right Way)

First things first - load your world and pause the game. Don't rush this part like I did during my first attempt. Hit Esc and click "Open to LAN":

1. Choose game mode (Survival, Creative, etc.)
2. Toggle "Allow Cheats" if needed
3. Critical step: Change port from default to your preferred number (like 25575 or 30000)
4. Click "Start LAN World"

Watch the chat like a hawk! You'll see:
[Server] Local game hosted on port 25575
That port number (in this example 25575) is what your friends need.

Finding Your Host IP Address

This trips up so many people. Here's how to find it without third-party tools:

You'll get something like 192.168.1.15 - that's your host IP. Write it down because you'll need to share it.

Joining the Game (Guest Steps)

Here's where knowing how to connect to LAN world Minecraft with port 1.21.5 gets real:

1. Open Minecraft 1.21.5 on guest computer
2. Go to Multiplayer screen
3. Click "Direct Connect" or "Add Server"
4. Enter address in this format: 192.168.1.15:25575
   (Replace with actual host IP and port)

That colon between IP and port isn't optional. Forget it and nothing happens.

Sometimes the LAN game appears automatically in the server list. But in my experience with 1.21.5, this only works about 60% of the time when using custom ports.

Firewall Configuration: The Silent Killer

This is where 90% of attempts fail. Firewalls block unknown connections by default.

Windows Firewall Fix

Search for "Windows Defender Firewall" → "Allow an app through firewall" → Change settings → Find "javaw.exe" (C:\Program Files\Java\jdk-21\bin) and "Minecraft Launcher" → Check both Private and Public boxes.

Better yet, create a rule:

1. Go to "Advanced settings"
2. Right-click Inbound Rules → New Rule
3. Choose Port → TCP → Specific ports: enter your port (ex: 25575)
4. Allow the connection → Select all profiles
5. Name it "Minecraft Port 25575"

I can't stress this enough - restart both computers after making firewall changes. Windows loves to pretend changes applied immediately when they really didn't.

Advanced Port Management Table

When dealing with multiple Minecraft instances or other services:

Router Settings That Actually Matter

For local connections, router configuration usually isn't needed. But if you're having issues:

• Disable AP Isolation in wireless settings (creates separate networks for each device)
• Enable UPnP (Universal Plug and Play)
• Check if your router has "Gaming Mode" - enable it

Honestly? I've never needed port forwarding for LAN play despite what some guides say. That's for internet connections.

Connection Troubleshooting: Real Fixes That Work

Last month my nephew kept disconnecting every 10 minutes. Turned out his laptop's network adapter was powering down to save battery.

Essential Network Tools I Actually Use

These free tools saved me countless hours:

• Angry IP Scanner - Finds all devices on network including their IPs
• Simple Port Tester - Checks if specific ports are open
• WinMTR - Network diagnostics tool
• GlassWire - Visual firewall monitoring

With Simple Port Tester, you enter the port number and hit "Test" - green check means it's open. If red, your firewall is blocking.

Why Version 1.21.5 Changes Things

Since 1.19, Mojang tweaked LAN discovery protocols. Some observations:

• Custom ports work more reliably than older versions
• Automatic discovery seems less consistent
• Direct IP connection is now the most stable approach
• Firewall handling improved but still problematic

Honestly? I think they overcomplicated what should be simple local play. But at least it's more secure.

Common Mistakes I've Made (So You Don't Have To)

• Using public IP instead of local IP (192.168.x.x not 76.x.x.x)
• Forgetting the colon in IP:PORT format
• Different network segments (wired vs wireless on guest network)
• Antivirus blocking Java (add exceptions in AV settings)
• Thinking port forwarding was needed (it's not for LAN)

FAQs: How to Connect to LAN World Minecraft with Port 1.21.5

Why doesn't automatic LAN detection work in 1.21.5?

Network discovery protocols can be flaky across different router brands. Always note the port number from chat and use direct connect with IP:PORT for reliability.

Can I use domain names instead of IP addresses?

Yes! Create a local DNS entry or use the host computer name like DESKTOP-PC:25575. Sometimes works better than IPs that occasionally change.

Why can't I connect even with correct IP and port?

90% of the time it's firewall related. Create both TCP and UDP rules for your port. Disable third-party antivirus temporarily to test. Check if any VPN is blocking local traffic.

How many players can join a LAN world?

Technically unlimited, but practically limited by your network and PC. With WiFi, I've seen lag with more than 8 players. Use Ethernet for larger groups. Performance tanks when hosting and playing on same machine.

Does this work between Windows and Mac?

Absolutely! Played last week with my wife on MacBook and my Windows desktop without issues. Just ensure identical Minecraft versions and proper firewall configuration on both systems.

Why use custom ports at all?

Great question! Main reasons: multiple worlds on same network, bypassing ISP restrictions, or avoiding conflicts with other apps running servers. Though honestly, default ports usually work fine if you're not doing anything fancy.

When All Else Fails: Nuclear Options

If you've tried everything and still can't connect:

1. Temporarily disable all firewalls (Windows Defender + third-party)
2. Connect both devices via Ethernet to same router/switch
3. Use hotspot from one computer
4. Try alternative connection method like Hamachi (free version works)

Once had a mysterious case where only restarting the router worked after hours of troubleshooting. Networking can be weird like that.

Final thought? Learning how to connect to LAN world Minecraft with port 1.21.5 seems complex at first, but becomes second nature. Last week I set up a 5-player LAN party in under 10 minutes. You'll get there too - just grab some snacks for the troubleshooting journey!