chapter 33: Networking

Question 1

Internet Protocol (IP)

Answer 1

A numeric address that uniquely identifies a computer on the internet. ex: 130.254.204.33

The IP is a low-level protocol for delivering data from one computer to another across the internet in packets.

Question 2

What makes an IP address?

Answer 2

four dotted decimal numbers between 0 and 255

ex: 130.254.204.33

Question 3

What is a domain name?

Answer 3

An identification string … Domain names serve as humanly memorable names for Internet participants, like computers, networks, and services.

www.google.com

“.com” is the top-level domain name. “google.com” is the domain name registered to google, and “google” is considered a second-level domain name. the “www” is the name of the web server (web host server) at the google.com domain.

www.google.com is a “fully qualified domain name (FQDN)”

Question 4

what is a domain name server? (DNS)

Answer 4

a domain name server on the internet translates host names into IP addresses.

when a computer contacts google.com, it first asks the DNS to translate this domain name into a numeric IP address and then sends the request using the IP address.

Question 5

What two higher-level protocols are using in conjunction with the Internet Protocol (IP) used to deliver data from one computer to another?

Answer 5

• Transmission Control Protocol (TCP)

- User Datagram Protocol (UDP)

Question 6

What does TCP stand for and what does it do?

Answer 6

-Transmission Control Protocol (TCP)

enables two hosts to establish a connection and exchange streams of data

guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

stream-based communcations use TCP

Question 7

What does UDP stand for and what does it do?

Answer 7

-User Datagram Protocol (UDP)

UDP is a standard, low-overhead, connectionless, host-to-host protocol that is used over the IP.

UDP allows an application program on one computer to send a datagram to an application program on another computer.

packet-based communications use UDP

Question 8

What kinds of communication does java support, stream or packet?

Answer 8

java supports stream-based and packet-based.

however, TCP can detect lost transmissions and resubmit them. UDP cannot guarantee lossless transmission, so stream-based communication (TCP) is usually used.

Question 9

What java class enables us to create a server socket?

Answer 9

ServerSocket

Question 10

What java class enables us to create a client socket?

Answer 10

Socket

Question 11

How do two programs on the Internet communicate with one another?

Answer 11

Two programs on the internet communicate through a server socket and a client socket using I/O streams.

Question 12

What is a socket?

Answer 12

A socket is an endpoint of logical connections between two hosts and can be used to send and receive data.

java treats socket communications much as it treats I/O operations; thus, programs can read from or write to sockets as easily as they can read from or write to files.

Question 13

How do the client and server communicate?

Answer 13

the client and the server communicate through sockets

Question 14

How do we establish a server?

Answer 14

We must create a server socket and attach it to a port.

Question 15

What is a port?

Answer 15

A port is where the server listens for connections.

It identifies the TCP server on the socket.

Question 16

What do port numbers range from?

Answer 16

0 - 65,536

Question 17

What port numbers are reserved for privileged services?

Answer 17

0 - 1024

Question 18

After the server accepts the connection, how is communication between server and client conducted?

Answer 18

It is the same as for I/O streams.

Question 19

Is it better to use text I/O or binary I/O? Why?

Answer 19

It is better to use binary I/O because text I/O requires encoding and encoding. Binary I/O improves performance.

Question 20

what java package should you import when writing java network programs?

Answer 20

java.net

Question 21

When a client connects to the server, a socket is created on the client. The socket has its own local port. How do we select the port number?

Answer 21

The JVM automatically chooses an available port to create a socket for the client.

Question 22

What class can we use to find out who is connecting to the server?

Answer 22

InetAddress

Question 23

How does java handle more than one client?

Answer 23

The connection to each client is handled by one thread.

A while loop creates a thread for each connection. pg. 1185

This makes it a multi-thread server.

Question 24

What classes do we use to send and receive objects?

Answer 24

ObjectOutputStream

ObjectInputStream

Question 25

What must we do to an object in order to enable passing?

Answer 25

The object must be serializable

implements java.io.Serializable

Question 26

What method enables a server Socket to listen for client connections?

Answer 26

accept()

Question 27

How does the client request a connection to a server?

Answer 27

the client requests a connection to a server by using

new Socket(serverName, port) to create a client socket.

Question 28

What classes can we use to get information about a web resource?

Answer 28

URL

URLConnection

Question 29

Break down this web address into its parts:

http://games.yahoo.com:80/games/login2?page=ch

Answer 29

protocol: http

host address: games.yahoo.com

server port number: 80

path to the resource file: games/login2?page=ch