Csc 240 - Chapter 3

Front 1

socket API

Back 1

Socket Application Programming Interface.

Front 2

Stream Paradigm

Back 2

stream denotes a paradigm in which a sequence of bytes flows from one application program to another. Internet's mechanism arranges two streams between a pair of communicating applications, one in each direction. It does not guarantee that the chunks of bytes passed to a receiving application correspond to the chunks of bytes transferred by the sending application.

Front 3

Message Paradigm

Back 3

It allows unicast, multicast, or broadcast delivery. Does not make any guarantees about the order in which the messages are delivered or whether a given message will arrive.

Front 4

Connection-oriented

Back 4

The service operates analogous to a telephone call: before they can communicate, two applications must request that a connection be created.

Front 5

Client-Server Model

Back 5

A form of interaction known as the client-server model. One application, known as a server, starts first and waits contect. The other application, known as a client, start second and initiates the connection.

Front 6

Internet

Back 6

Although it povides basic communication, the Internet does not initiate contact with, or accept contact from, a remote computer; application programs known as a clients and servers handle all services.

Front 7

Server

Back 7

Formally, the term refers to a program that waits passively for communication, and not to the computer on which it executes. However, when a computer is dedicated to running one or more server programs, the computer itself is sometimes called a server.

Front 8

Client

Back 8

Typically, a client sends a request to a server, and the server returns a response to the client.

Front 9

Multiple Clients and Multiple Servers

Back 9

Computers can run multiple applications at the same time. 1) single client 2) single server 3) Multiple copies of a client that contact a given server. 4) Multiple clients that each contact a particular server. 5) Multiple servers, each for a particular service.

Front 10

Identifying A Computer

Back 10

Each computer in the Internet is assigned a unique 32-bit identifier known as an Internet Protocol Addres (IP Adrress).

Front 11

Domain Name System (DNS)

Back 11

Makes server identification easy for the humans, each comptuer is also assigned a DNS.

Front 12

Identifying A Service

Back 12

Each service available in the Internet is assigned a unique 16-bit identifier known as a Protocol Port Number (port number). Email = port number 25. Web = port number 80.

Front 13

Concurrent Servers

Back 13

A server uses more than one thread of control to handle multiple clients at the same time.

Front 14

peer-to-peer (p2p)

Back 14

data is distributed equally among a set of N servers, and each client request is sent to the appropriate server. Because a given server only provides 1/N of the data, the amount of traffic betwee a server and the Internet is 1/N as much as in the single-server architecture.

Front 15

Application Program Interface (API)

Back 15

The interface an application uses to specify communication

Front 16

I/O socket

Back 16

Applications can use the read and write operations for socket I/O or I/O to a file. When an application creates a socket, the operating system returns a small integer descriptor tha the application uses to reference the socket.

Front 17

Advantages of Sockets

Back 17

Advantage of the socket approach is that most functions have three or fewer parameters; the disadvantage is that a programmer must remember to call multiple functions when using sockets.

Front 18

Protofamily

Back 18

specifies the protocol family to be used with the socket.

Front 19

getpeername

Back 19

Server command used to obtain the address of the remote client that initiated the connection

Front 20

gethostname

Back 20

Client or server command used to obtain information about the comptuer on which it is running.

Front 21

setsockopt

Back 21

stores values in a socket's options

Front 22

getsockopt

Back 22

obtain current option values.

Front 23

gethostbyname

Back 23

returns the Internet address for a comptuer given the computer's name

Front 24

gethostbyaddr

Back 24

given an IP address for a computer, it returns the computer's name.

Front 25

socket reference count

Back 25

mechanism to control each socket. When a socket is first created, the system sets the socket's reference count to 1, and the socket exists as long as the reference count remains positive. When a program creates an additional thread, the thread inherits a pointer to each open socket the program owns, and the system increments the reference count of each socket by 1. When a thread calls close, the system decremetns the reference count for the socket: if the reference count has reached zero, the socket is removed.