Make sure the web site or other kind of
Internet server you run at home is always available to the world. If
you run your own web server, mail server, or other kind of server at
home and are connected to the Internet via a cable modem or DSL
modem, people frequently might not be able to connect to your
server. That's because, typically, broadband ISPs assign you a
dynamic IP address that changes regularly, even if you don't turn
off your PC. Because your IP address constantly changes, there is no
way for people to connect to you. One day its IP address might be
66.31.42.96, the next it might be 66.41.42.136, and if people don't
know your server's current IP address they won't be able to find it.
You won't be able to solve the problem by getting your own domain
(such as www.gralla.com) and publishing that because DNS
servers won't be able to keep track of your changing IP address
either. If people type in your domain name, the servers won't be
able to report on your IP address and again, your server won't be
able to be reached. There is a way to solve the problem, however:
you can map your server's hostname to a dynamic IP address. When you
do this, it doesn't matter that your IP address changes; when people
type in your web site's URL, they will be forwarded to your new IP
address automatically. You can do this for free by signing up with a
service that provides automatic mapping. A number of services will
do it for free, such as No-IP.com (http://www.no-ip.com).
When you sign up for the service, you choose a hostname for your
server and give that hostname out to people who want to connect to
the server. Whatever name you choose will end in
.no-ip.comfor
example, grallasite.no-ip.com. After you get your hostname, you
download client software that continually monitors your IP address.
It reports on your server's current IP address to the No-IP.com
site. Whenever the IP address changes, it reports that new IP
address to the site. The client checks your IP address every three
seconds. Whenever a PC tries to connect to your server, it first
goes to a No-IP.com server, which looks up your server's current
address and then redirects the PC to your server, based on your
current IP address. The person contacting your site will not have to
do anything different from what he normally does; he just types in
your URL and is connected to your site. If you own a domain and want
to map that hostname to a dynamic IP address instead of using a No-IP.com
address, you'll have to sign up for No-IP.com's No-IP Plus service
for $24.95 a month. If you're using a router at home to share
Internet access among several PCs, you might run into problems using
the service. Many routers use NAT, in which all PCs on the network
share a single external Internet address but are assigned internal
network addresses. The No-IP.com client will track your external
address, but because that single address is used by all PCs on the
network, not just the server, incoming traffic won't be routed to
your server. You can fix the problem by using the port forwarding
feature of your router to send the incoming traffic to the server
[Hack #50] . You might run into another problem as well: when you
try to test your server by connecting to it from a PC inside your
network, you might not be able to connect to it. That's because you
might not be able to connect to the external IP address from inside
the network. If this happens, the only solution is to connect to the
site from a PC outside your network or ask a friend to connect to
it. One more thing to watch out for: if you're behind a firewall,
the No-IP.com client might have trouble connecting back to the No-IP.com
site to report on your changing IP address. If you're using a
firewall like ZoneAlarm [Hack #78] or a similar one that blocks
outbound connections, tell it to allow the client to make outbound
connections. Also, depending on the firewall you use, you might need
to configure it to open TCP port 8245 because that's the port the
client uses to contact No-IP.com with your new IP address.
