Sign in to follow this  

Port forwarding guide

Recommended Posts

Here's basically how this networking thing works.

(Or you can skip straight ahead to "Step 0" if you want.)

(If you don't have a router, then you don't even need to do much: just do "Step 0" and "Step 1")

A Typical Network Setup

(Note: in the past few years, it's become common for ISPs to provide a single device that works as the modem and the router...)

You have a cable or DSL modem or something. It connects to the internet. It has its own IP address. To the rest of the internet, all the computers on your network appear to be coming from that one IP address. If you're curious, you can find out your modem's IP address by going to

Attached to that modem, you probably have a router. Common brands are Linksys (or Cisco), D-Link, NetGear, Belkin... The router allows you to split the internet connection to multiple computers. Lots of them are wireless these days... Routers direct network traffic.

The router creates its own internal home network for you. Typically, the IP address of the router is or

You connect your computer to the router (either with a cable or by connecting to it wirelessly). The router gives your computer an IP address on the router's "subnet." Usually the first computer to connect will be given (or ..0.100). The second computer will be .101, and so on. However, if your computer reboots and the router doesn't realize it, it may give your computer a different IP address next time, say .103.

Your computer will usually have a firewall on it, like Windows Firewall, Zone Alarm, or Norton. This will attempt to block incoming connections.

What the Problem Is

When someone tries to connect to your computer from the internet, they enter the IP address of your modem, not of a particular computer. The connection attempt goes straight through to the router. However, the router thinks "who's this bum? you want to mess with one of my computers? get lost!" and it ignores the connection for safety reasons. Even if it didn't think that, it wouldn't know which computer to send the connection to, anyway. We're going to fix that.

How to Fix the Problem

We can tell the router to accept a connection attempt on a particular port and to forward that connection attempt to a particular IP address on the internal network.

There is a problem, though... what if you reset your computer and the internal IP address changes? To fix that, we also need to tell our computer to always be the same IP address, instead of letting the router tell it what IP address to be. This is called a "static IP."

Also, the firewall on your computer may block the connection. We need to tell it to allow the connection. Many firewalls will tell you when a connection comes in and ask you whether to accept or ignore it.

Step 0: Find Your Modem's IP Address

AKA "external ip address" or simply "ip address"

Just go to and it'll tell you what it is. "My IP Address is:...."

This is the address you give to people so they can connect to you.

Step 1: How To Unblock the p2p Port

The Gens p2p port is 27886.

The ZSNES port is.. i don't know, I don't use it. 7845 ?

If you are using Windows Firewall: - For Step 5 - use port 27886 for Gens or whatever it is for ZSNES.

- For Step 6 - use TCP this time, then do the steps again for UDP

- For Step 7 - ignore step 7

Repeat the steps again, but use UDP for Step 6 the second time.

If you are using another firewall, hopefully it will just pop up a message asking you to allow the connection when trying to play a p2p game. Zone Alarm does this. I haven't used many others.

Step 2: How to Set Up a Static IP Address

Do this:

I recommend setting the final number to something like .110, not .100/.101... This reduces the change of a conflict caused by other computers/devices on your network taking over your static IP when your computer is off.

NOTE: Using a static IP with a laptop you take to networks outside your home can cause trouble. See the "Potential Problems" section at the end of this post.

Step 3: How to Forward the p2p Port

Find the model number of your router. It's often on a sticker on the underside of the router. Find it in this router list:

Click the link for your router.

Right above the big list of games, it'll say "If you do not see the program you are forwarding ports for, be sure to visit our Default Guide for this router." Click the "Default Guide" link (they really should make it more prominent on the page).

You need to use two numbers: your static IP, and the port to open (27886).

When it comes to the UDP/TCP/Both, try to use Both if available. If not, set it up twice, once for each option.

Potential Problems:

If you set up a static IP on your wireless connection and then bring your computer to a friend's house or some free wifi, the IP address might be invalid on that network. You need to go back to that Properties page with all the IP addresses and set it back to '"Obtain an IP address automatically". This is quite likely on free wifi.

Sometimes the DNS server(s) change. If your internet stops working some day on just your static IP computer, then revert to automatic IP and check to see if the DNS servers are still the same. If they're different, just set up static IP again with the new DNS servers.[/url]

Edited by smozoma

Share this post

Link to post
Share on other sites

if you use this, please tell me if it works or doesn't work for you, so I can update it if it needs more information

Share this post

Link to post
Share on other sites
if you use this, please tell me if it works or doesn't work for you, so I can update it if it needs more information

I have a question about this

does it make a difference if your playing on laptop?

Share this post

Link to post
Share on other sites
I have a question about this

does it make a difference if your playing on laptop?

Not really.

The one issue with laptops, will be that you're more likely to bring a laptop with you somewhere and use a different wifi network. when you move to a new network, you might not be able to connect due to the static IP stuff. in which case you just need to disable static ip temporarily... That happened to me a few weeks ago when i couldn't connect to an airport network and didn't know what was going wrong.. 10 minutes later I remembered i had a static IP and that was the problem.

another option is to not use static IP at all, and just change the port forwarding if your laptop's IP address changes.

the advantage of hamachi is that you don't have to care about any of this ip address stuff... but you have to install extra software and worry about finding a room both you and your opponent can join.

Share this post

Link to post
Share on other sites

bump due to the start of the classic league season and there being lots of new guys

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this