Java Reference
In-Depth Information
C H A P T E R 9
Interacting with Networks and Databases
Youhavethreetargetsforaccessingdatathat'sexternaltoanapplication:filesystem,net-
work,anddatabase.
Chapter8
introducedyoutofilesystem-orienteddataaccess,whereas
this chapter introduces you to data access via networks and databases.
Interacting with Networks
A
network
isacollectionofinterconnected
nodes
(computersandperipherals[e.g.,print-
ers])thatcansharehardwareandsoftwareamongusers.An
intranet
isanetworkwithin
anorganizationandan
internet
isanetworkthatlinksorganizationstogether.The
Inter-
net
is the global network of networks.
Note
IntranetsandinternetstypicallyuseTransmissionControlProtocol(TCP),User
Datagram Protocol (UDP), and Internet Protocol (IP) to communicate between nodes.
TCP is a two-way communication protocol, UDP is a one-way communication pro-
tocol,andIPisthefundamentalcommunicationprotocoloverwhichTCPandUDPper-
form their communication tasks. TCP, UDP, and IP are combined with other protocols
into a model known as TCP/IP (see
http://en.wikipedia.org/wiki/TCP/
The
java.net
packagesuppliesassortedclassesthatsupportTCP/IPcommunication
between
processes
(executingapplications)thatarerunningonthesameordifferent
hosts
(computer-basedTCP/IPnodes).Afterintroducingyoutoeachoftheseclasses,thissec-
tion presents authentication and cookie management.
Communicating via Sockets
A
socket
isanendpointinacommunicationslinkbetweentwoprocesses.Theendpoint
consistsofan
IP address
,whichidentifiesahost,anda
port number
,whichidentifiesa
process running on that network node.
