Prepared By E.Musa Alyaman1 Chapter 3 Internet Addressing

Prepared By E.Musa Alyaman2 Chapter 3 Outline Hosts Internet addresses Next Generation Internet IPv4 Class A,B and C addresses Domain Name System (DNS) Creating InetAddresses Java 1.4 Added Methods Getter Methods Address Types Object Methods Chapter 3 Highlights

Prepared By E.Musa Alyaman3 Hosts Devices connected to the Internet are called hosts Most hosts are computers, but hosts also include routers, printers, fax machines,etc.

Prepared By E.Musa Alyaman4 Internet addresses Every host on the Internet is identified by a unique, four-byte Internet Protocol (IP) address. This is written in dotted quad format like where each byte is an unsigned integer between 0 and 255. There are about four billion unique IP addresses, but they aren’t very efficiently allocated

Prepared By E.Musa Alyaman5 Next Generation Internet The solution is IPv6 which uses 128 bit addresses Improves services such as multicasting and secure communication Not yet widely deployed by ISPs Well written Java software should move to IPv6 without modification/recompilation this is one benefit of abstracted APIs

Prepared By E.Musa Alyaman6 IPv4 Each 32 bit IP number consists of two components: –The network address The unique international address of the network –The host address The unique address of a specific host in the net There are three classes of network address denoted class ‘A’, ‘B’ and ‘C’

Prepared By E.Musa Alyaman7 Class A,B and C addresses Class A Class B Class C Network Address Byte Host Address Byte

Prepared By E.Musa Alyaman8 Domain Name System (DNS) Numeric addresses are mapped to names like or mail.msn.com by DNS. Each site runs domain name server software that translates names to IP addresses and vice versa DNS is a distributed system

Prepared By E.Musa Alyaman9 IP Addresses and Java Java has a class java.net.InetAddress which abstracts network addresses Serves three main purposes: –Encapsulates an address –Performs name lookup (converting a host name into an IP address) –Performs reverse lookup (converting the address into a host name)

Prepared By E.Musa Alyaman10 Creating InetAddresses There are no public InetAddress() constructors. Arbitrary addresses may not be created. All addresses that are created must be checked with DNS

Prepared By E.Musa Alyaman11 Ways to create InetAddress objects public static InetAddress getByName(String host) throws UnknownHostException public static InetAddress[ ] getAllByName(String host) throws UnknownHostException public static InetAddress getLocalHost() throws UnknownHostException

Prepared By E.Musa Alyaman12 Java 1.4 Added Methods Java 1.4 adds two more factory methods that do not check their addresses with the local DNS server. The first creates an InetAddress object with an IP address and no hostname. The second creates an InetAddress object with an IP address and a hostname. public static InetAddress getByAddress(byte[ ] address) throws UnknownHostException public static InetAddress getByAddress(String hostName, byte[] address) throws UnknownHostException

Prepared By E.Musa Alyaman13 Getter Methods They return the hostname as a string and the IP address as both string and a byte array public String getHostName() public byte[ ] getAddress() public String getHostAddress()

Prepared By E.Musa Alyaman14 Address Types Public boolean isAnyLocalAddress() Public boolean isLoopbackAddress() Public boolean isLinkLocalAddress() Public boolean isSiteLocalAddress() Public boolean isMulticastAddress() Public boolean isMCGloabl() Public boolean isMCNodeLocal(( Public boolean isMCLinkLocal() Public boolean isMCSiteLocal() Public boolean isMCOrgLocal()

Prepared By E.Musa Alyaman15 Object Methods Public boolean equals (Object o) Public int hashCode () Public String toString ()

Prepared By E.Musa Alyaman16 Inet4Address and Inet6Address Public final class Inet4Address extends InetAddress Public final class Inet6Address extends InetAddress

Prepared By E.Musa Alyaman17 Using InetAddress objects import java.net.InetAddress; import java.net.UnknownHostExcepion; public static void main(String[] args) { try { InetAddress inet1 = InetAddress.getByName("asp.ee.uwa.edu.au"); System.out.println( "HostAddress=" + inet1.getHostAddress()); InetAddress inet2 = InetAddress.getByName(" "); System.out.println("HostName=" + inet2.getHostName()); if (inet1.equals(inet2)) System.out.println("Addresses are equal"); } catch (UnknownHostException uhe) { uhe.printStackTrace(); }

Prepared By E.Musa Alyaman18 Chapter Highlights In this chapter, you have learned: About the Domain Name System (DNS) and domain name suffixes (such as.com) About the structure of an IP address and the various classes of IP addresses About the InetAddress class and its various methods