[ Home ] [ Up ] [ Network Communication Protocols ] [ Host Names & IP Addresses ] [ Domains ] [ Transport Protocols ] [ Ports ] [ The InetAddress Class ]

Every computer on the Internet has at least one host name and at least one IP address. IP addresses provide a unique identifier for each machine.

Host names provide a convenient name for human consumption, and there is a mapping between a host name and an IP address. The mapping of host name to IP address is, in general, 1:n. That is, a host machine may have one or more IP addresses. Typically, a machine has one IP address for each network interface card (NIC) it has installed.

IP addresses are 32-bit numbers which usually are represented like: 207.46.130.14, where each group of digits represents 8 bits of the 32-bit number, and is usually expressed in decimal.

See later for how to discover the IP address for a given host.

There is a special host name, localhost, which translates to a special IP address, 127.0.0.1, which represents the local machine.