Socket Presentation

7/31/2019 Socket Presentation

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SOCKETS

1


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COMPUTER NETWORK

A computer networkis aninterconnected collection of autonomouscomputers.


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WHAT A NETWORK INCLUDES

Address: byte-string that identifies a node usually unique

Routing: process of forwarding messages

to the destination node based on itsaddress.

Protocol: set of rules used forcommunication.


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BASIC PARADIGM FORCOMMUNICATION

Establish contact (connection).

Exchange information (bi-directional).

Terminate contact.


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ELEMENTS OF C-S COMPUTING

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Network

Reque

st

R

esult

a client, a server, and network

ClientServer

Client machine

Server machine


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CLIENT-SERVER COMMUNICATION

Client sends a request to the server

Server accepts the request and establish a connection


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SOCKETS

A socket is defined as an endpoint forcommunication.

Concatenation of IP address and port

A socket pair (local IP address, local port,foreign IP address, foreign port) uniquely

identifies a communication.

The socket 161.25.19.8:1625 refers to port1625 on host 161.25.19.8


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TWO ESSENTIAL TYPES OF SOCKETS

SOCK_STREAM

TCP reliable delivery

in-order guaranteed

connection-oriented

Bidirectional Stream flow of data

SOCK_DGRAM

UDP

unreliable delivery

no order guarantees

no notion of connection

app indicates dest. foreach packet

can send or receive

Datagram format

App

socket3 2 1

Dest.

App

socket3 2 1

D1

D3

D2


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SOCKET FUNCTIONAL CALLS

socket (): Create a socket

bind(): bind a socket to a local IP address andport #

listen(): passively waiting for connections connect(): initiating connection to another socket

accept(): accept a new connection Write(): write data to a socket Read(): read data from a socket sendto(): send a datagram to another UDP socket

recvfrom(): read a datagram from a UDP socket close(): close a socket (tear down the connection)


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CONNECTION-ORIENTED EXAMPLE (TCP)

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Server

Socket()

Bind()

Client

Socket()

Listen()

Accept()

Recv()

Send()

Connect()

Send()

Recv()

Block until

connect

Process

request

Connection Establishmt.

Data (request)

Data (reply)

Bind()


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CONNECTIONLESS EXAMPLE (UDP)

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Server

Socket()

Bind()Client

Socket()

Recvfrom()

Sendto()

Bind()

Sendto()

Recvfrom()

Block until

Data from

client

Process

request

Data (request)

Data (reply)


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JAVA SOCKETS

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ServerSocket(1254)

Socket(128.250.25.158, 1254)

Output/write stream

Input/read stream

It can be host_name like mandroo.cs.mu.oz.au

Client

server


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Socket Presentation

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