Dealing with port forwarding

Dealing with port forwarding
After you have your gaming PC or game console assigned an IP address and
you’re connected to the Internet, you might very well be ready to start playing
games. Our advice: Give it a try and see what happens. Depending upon
the games that you play, any additional steps might not be needed.
The steps that we’re about to discuss shouldn’t be required for a game console.
And although we haven’t checked out every single game out there, we
haven’t run into any incidences where you need to get involved with the port
forwarding that we’re about to discuss with a game console. After you get
your console assigned an IP address and connected to the Internet, you
should be ready to start playing. If you have an older router that doesn’t
work well with console games, you might consider putting your console on
the router’s DMZ as we discuss in the upcoming section “Setting Up a
Demilitarized Zone (DMZ).”
If, however, your games don’t work, you might need to get involved in configuring
the firewall and Network Address Translation (NAT). As we discuss in
Chapters 5 and 9, home network routers use a system called NAT to connect
multiple devices to a single Internet connection. What NAT does, basically, is
translate between public Internet IP addresses and internal IP addresses on
your home’s network. When a computer or other device is connected to your
home network (wirelessly or even a wired network), the router assigns it an
internal IP address. Similarly, when your router connects to the Internet, it’s
assigned its own public IP address: that is, its own identifying location on the
Internet. Traffic flowing to and from your house uses this public IP address to
find its way. After the traffic (which can be gaming data, an e-mail, a Web
page . . . whatever) gets to the router, the NAT function of the router figures
out to which PC (or other device) in the house to send that data.
One important feature of NAT is that it provides a firewall functionality for
your network. NAT knows which computer to send data to on your network
because that computer has typically sent a request over the Internet for that
bit of data. For example, when a computer requests a Web page, your NAT
router knows which computer made the request so that when the Web page
is downloaded, it gets sent to the right PC. If no device on the network has
made a request — meaning that an unrequested bit of data shows up at your
public IP address — NAT doesn’t know where to send it. This provides a
security firewall function for your network because it keeps this unrequested
data (which could be some sort of security risk) off your network.
NAT is a cool thing because it lets multiple computers share a single public IP
address and Internet connection and because it helps keep the bad guys off
your network. NAT can, however, cause problems with some applications
that might require this unrequested data to work properly. For example, if
you have a Web server on your network, you would rightly expect that
people would try to download and view Web pages without your PC sending
them any kind of initial request. After all, your Web server isn’t clairvoyant.
(At least ours isn’t!)
Gaming can also be an application that relies upon unrequested connections
to work properly. For example, you might want to host a game with your
friends on your PC, which means that their PCs will try to get through your
router and connect directly with your PC. Even if you’re not hosting the
game, some games will send chunks of unrequested data to your computer as
part of the game play. Other applications that might do this include things
such as audio and video conferencing programs (such as Windows
Messenger) and remote control programs (such as pcAnywhere).
In order to get these games (or other programs) to work properly over your
wireless home network and through your router, you need to get into your
router’s configuration program and punch some holes in your firewall by setting
up NAT port forwarding.
Of the many routers out there, they don’t all call this port forwarding. Read
your manual. (Really, we mean it. Read the darn thing. We know it’s boring,
but it can be your friend.) Look for terms like special applications support or
virtual servers.
Port forwarding effectively opens a hole in your firewall that will not only
allow legitimate game or other application data through but might also let the
bad guys in as well. Only set up port forwarding when you have to and keep
an eye on the logs. (Your router should keep a log of who it lets in — check
the manual to see how to find and read this log.) We also recommend that
you consider using personal firewall software on your networked PCs (we like
ZoneAlarm, www.zonelabs.com) and that you keep your antivirus software
up to date.
Some routers let you set up something called application triggered port forwarding,
which basically allows your router to look for certain signals coming
from an application on your computer (the triggers), and then enable port
forwarding. This is a more secure option, if it’s available to you, because
when the program that requires port forwarding (your game, in this case) is
not running, your ports are closed. They only open when the game (or other
application) requires them to be opened.
When you set up port forwarding on your router, you are selecting specific
ports (ports are actually a subsegment of an IP address — a computer with a
specific IP address will use different numbered ports to connect different
applications to the network) and sending any and all incoming requests using
those ports to a specific computer or device on your network. When you get
involved in setting up port forwarding, you’ll notice two kinds of ports: TCP
(Transmission Control Protocol) and UDP (User Datagram Protocol). These
names relate to the two primary ways by which data is carried on the
Internet, and you might have to set up port forwarding for both TCP and UDP
ports, depending upon the application.
Every router or access point will have its own unique system for configuring
port forwarding. Generally speaking, you’ll find the port forwarding section of
the configuration program, and simply type the port numbers you want to
open up into a text box on the screen. For example, Figure 12-3 shows port
forwarding being configured on a Siemens SpeedStream router/access point.
As we mention earlier, ports are assigned specific numbers. And to get some
gaming applications to work properly, you’ll need to open (assign) port forwarding
for a pretty big range of port numbers. The best way to find out
which ports need to be opened is to read the manual or search the Web page
of the game software vendor. You can also find a relatively comprehensive list
online at practicallynetworked.com/sharing/app_port_list.htm.

Figure 12-3:
Setting up
port
forwarding.
If your router is UPnP-enabled (Universal Plug and Play, a system developed
by Microsoft and others, that — among other things — automatically configures
port forwarding for you) and the PC game that you’re using uses
Microsoft’s DirectX gaming, the router and the game should be able to talk to
each other and automatically set up the appropriate port forwarding. Just
make sure that you enable UPnP in your router’s configuration system — this
will usually be a check box in the router’s configuration program.