Dynamic Host Configuration Protocol (DHCP). DHCP is a protocol used by a computer (or "host" in Internet parlance) to obtian an IP address to use in communicating with other computers (hosts). The IP address the host is given may change from time to time (it is dynamic) and so the host is not normally addressable from the Internet. That is, the a host on the open Internet cannot establish a connection to the host using DHCP since it's address is unknown (or may have changed since its last known value).
There are two ways to work around the fact that a host using DHCP will change its IP address. The first is to use a static ip address. The second is to use dynamic DNS.
