Linux Client-Server Overview

7/25/2019 Linux Client-Server Overview

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EE 367LClient Server Lab

University of Hawaii EE 367L


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Outline Big piture

Client server para!ig"

#e"ote $le server Linu% operations

How to all a Linu% o""an! fro" a progra" e%e& '

How to get t(e output of a Linu% o""an! ) pipes How to all operations fro" a progra" for*& ' an! wait& '

+roesses

#e"ote $le server Client

#e"ote server

So*ets



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Server


-nternet&Clou!'

Stdin

Stdout

socket socket

> lsa.outhello.chello

Server


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Client Server +ara!ig"


Client

Serve&e/g/0 wi#euest servie&sen! o""an!'e/g/0 ls0 at0 "ov

#eplies to reueste/g/0 !ata t(at satis$est(e reuest

Listening for ran! t(en re

-ssues o""an!sfor servie


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Linu% o""an!s

Linu% o""an!s are e%eute! by software provLinu%

Syste" alls2 e%a"ples2 ls0 r"0 at0 ////

Lets suppose you wante! to write a progra" t(t(e ontents of your urrent !iretory on t(e pan

!isplay How !o you i"ple"ent 4ls5 fro" a progra"

Option 12 Use very basi syste" alls0 e/g/0 open&'0 wrea!& '0 to e"ulate 4ls5/ (is is basially writing t(e sfro" srat(

Option ,2 8ou an all 4ls5 using e%e& '0 or one of itsvariations University of Hawaii EE 367L


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e%el

Useful w(en you want to write a progra" : t(at Linu% o""an!s su( as 4r"50 4ls50 4p5

e%el an be use! to all t(ese o""an!s -t overwrites t(e e%isting proess wit( anot(er progra"

E%a"ple2 e%el&4;bin;ls50 4ls50 4)l50 &(ar ?irst para"eter is t(e progra" t(at overwrites t(e urrent pr

(e ne%t para"eters are w(at woul! nor"ally be type! by a

user2 ls )l Seon! para"eter is t(e $rst argu"ent in t(e argu"ent list0 i/e/

(ir! para"eter is t(e seon! para"eter in t(e argu"ent list0 i/

?ourt( para"eter in!iates t(ats t(e en! of t(e argu"ent list spara"eter list (as an arbitrary lengt(

not(er e%a"ple2 e%el&4;usr;bin;s(50 4s(50 4)50 4ls

(ere are variations su( as e%elp google to $n!University of Hawaii EE 367L


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E%a"ple


ain&'

%el&4;bin;ls50 4ls50 &(ar

Overwrite

ls

e! to !o "ore beause t(e original progra" is comple

ant a progra" toll a U=-: o""an!e !ata fro" t(e o""an! an! ontinue proessing


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Solution

Original progra" &4proess5' reates anot(er 4progra"

(e (il! progra" e%eutes 4e%el5

(e original is not overwritten an! ontinues to

(is is i"ple"ente! using t(e for*& ' syste" al -t reates a (il! proess w(i( is i!ential to t(e orig

proess

-f t(eyre i!ential opies0 (ow an a proess tell w(et(e (il! or parent



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+roesses +roess is a 4running progra"5 sort of a virtual o"pu

E%eutable o!e

Ie"ory for !ata0 e/g/0 global variables0 sta*0 (eap &for !yna"e"ory alloation'

C+U #egisters0 su( as general purpose registers0 progra" ounter0 status

registers0 ///

Jery si"ple o"puters run e%atly one proess E%a"ples2 signal proessing0 e"be!!e! syste"s

Keneral purpose o"puters an run "ultiple proesses(e proesses run li*e in!epen!ent virtual o"puters

Iultiple proesses are reate! by t(e operating syste"given proess -s &+-s'



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+roesses"ain&'Dw(ile&1' D if &fork( ) NN A' D ;< (il!

F else D ;< parent

F

FF

"ain&'Dw(ile&1' D if &fork( ) NN A' D ;< (il!

F else D ;< parent ;; parent o!e

FFF

"ain&'Dw(ile&1' D

if &fork( ) NN tas*1& '2 ;; e%it&E:-SU F else D ;< paren tas*,& '> wait& '>

FFF

Original parent processfor*&' returns +- of (il!

Child procefor*&' return


k& ' reates an i!ential opy of t(e proess0alle! a 4(il!5 proess/ So now t(ere is a (il!n! t(e 4parent5 &original' proessunning toget(erturns

A if its a (il! proess+- of (il! if its t(e parent

wait& ' will stop t(e proess until a (il!proess ter"inates


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+roesses

;

f!@A N rea!)en! of t(e pipef!@1 N write)en! of t(e pipe

8ou an write0 rea!0 lose

Be sure to reate a pipe before yo(il! an! parent (ave aess to t



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e%el

+rogra" : E%a"ple 12 wit(out pipe

Iain progra" alls for*& ' to reate a (il! C(il! alls e%el &4ls5//////'

C(il! is overwritten by 4ls5

(e output of 4ls5 goes to st!io0 w(i( by !efault is your ter"i

E%a"ple ,2 wit( pipe Iain progra" reates a pipe0 an! reeives $le !esriptors

Iain progra" &parent' reates a (il! C(il! re!irets st!io to t(e pipe using dup2

C(il! alls e%el&4ls5///' output goes t(roug( t(e pipe

+arent reeives t(e output t(roug( t(e pipe



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E%a"ple 1

"ain&'D

F

arent Child


"ain&'D

for*& '

F

"ain&'D

e%el progra"0 e/g/0 4ls5

F

Ov

C(il! will run 4ls50 w(i( now sen!soutput to st!io0 w(i( by !efault ist(e ter"inal

Output


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E%a"ple ,

"ain&'DListen to pipe+roess w(at o"esF

arent Child


"ain&'D!ake a pipe"ind #le descriptorsfork& 'F

"ain&'D#e!iret output fro" st!io to pipe using !up,e%el progra"0 e/g/0 4ls5F

pipe


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E%a"ple ,

"ain&'D$isten to pipe+roess w(at o"esF

arent Child


"ain&'DIa*e a pipeBin! $le !esriptorsfor*& 'F

"ain&'D%edirect output fro& stdio to pipe using dup2e%el progra"0 e/g/0 4ls5F

pipe


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E%a"ple ,

"ain&'DListen to piperocess what co&esF

arent Child


"ain&'DIa*e a pipeBin! $le !esriptorsfor*& 'F

"ain&'D#e!iret output fro" st!io to pipe using !up,e%el progra"0 e/g/0 4ls5F

pipeCo"Ove


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e%el0 et

(ere is a progra" pipe/ in t(e proPet t(at s(owto use e%el0 !up,0 an! pipes

#ea! it0 o"pile it0 an! run it



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Server


-nternet&Clou!'

Client '

socket socke

> lsa.outhello.chello

1. ser types *ls+2. Sends a &essage to server re,uesting *ls+

-. aits for a reply fro& /. 0ets reply and outputs to user

. $istening

. %eceivesan *ls+

3. 4xecutes5. Sends th

client '

6ey issue7 how do wetransport over thecloud


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?ile ransferypial syste" alls &to t(e operating syste"'

f! N fopen&4$lena"e50 4w5'>

Operating syste" reates a $le in t(e loal server &loal !is* !rive'

-t gives t(e $le an na"e 4$lena"e5 an! t(is is reoso"ew(ere by t(e operating syste"

Operating syste" assigns t(e $le a $le !esriptor n&f!'

?ro" t(is point0 t(e $le is referene! using f!

fprintf&f!0 4Hello worl!5'>

flose&f!'>

Even si"pler is write& ' an! rea!& '

#e"ote $les



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So*ets

wo types Strea& sockets

Long live! onnetion between two entities

Base! on t(e C+ protool

e8ll concentrate on this type of socke

atagra" so*ets

One "essage &!atagra"'

Base! on t(e U+ protool



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So*ets

-nternet =etwor*

&=etwor* Layer -+ protool'port N -+ a!!ress 1,/19/,A/A

C+ +orts

ppliations Client

C+ protool C

o"ew(ere/o"in na"e for t(eressin =a"e Syste" &=S' is use! to onvert a !o"ain na"e into a



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Co"ponents to set up a So*et Ket infor"ation for a so*et

Client

-+ a!!ress Converte! fro" a url0 su( as www/ee/(awaii/e!u w(i( re

servie

C+ port nu"ber

ype of so*et0 e/g/0 !atagra" versus strea"

ServerC+ port nu"ber

ype of so*et

Set up t(e so*et0 auire $le !esriptor f!

sen!;rev using f!



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So*ets getting t(e infor"atio geta!!rinfo&4www/e%a"ple/o"5 0 4(ttp50 Q(ints0

www/e%a"ple/o" is t(e (ost na"e &-+ a!!ress' to on

input Seon! para"eter is a port nu"ber )) input

lternatively0 you an use 4(ttp5 if its t(e port for t(e (ttp on

4(ints5 (as !ata t(at to be use! to set up t(e onnetio E%a"ples

(ints/aifa"ily N ?U=S+EC> ;; ont speify -+v. or -+v6

(ints/aiso*type N SOCRS#EI> ;; or SOCRK#I

(ints/aiags N -+SS-JE> ;; ssign loal (ost to -+ a!struture

4res5 is t(e output or results an! t(is is in a lin*e! list fouput

e (ttp2;;beeP/us;gui!e;bgnet;output;(t"l;"ultipage;sysalls/(t"lr t(ese syste" alls an! t(ere is an e%a"ple alle! s(owip/ t(at you an runin setion 9/1

http://beej.us/guide/bgnet/output/html/multipage/syscalls.htmlhttp://beej.us/guide/bgnet/output/html/multipage/syscalls.htmlhttp://beej.us/guide/bgnet/output/html/multipage/syscalls.html


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So*ets geta!!rinfo&4www/e%a"ple/o"5 05(ttp50 Q(ints

so*f! N so*et&res)Taifa"ily0 res)Taiso*type0

Taiprotool'> so*f! is t(e so*et $le !esriptor0 si"ilar to a $le !es

+oints to infor"ation nee!e! to set up a onnetion

o "a*e a onnetion0 so*f! nee!s to bin! itself to a pa!!ress;port

-t !epen!s on w(et(er it is a 4lient5 or 4server5



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Client)Server


Client Server

#euest

#eply-nitiates ransation

Client Server

#euest onnetionto a port : ; -+ a!!ress

+rovi!es its own port;-+ a!!r

#eply-nitiates onnetion

r

no -+ a!

G

re

sen!rev

sen!rev


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Client So*et geta!!rinfo&4www/e%a"ple/o"5 03.MA0 Q(ints0

so*f! N so*et&res)Taifa"ily0 res)Taiso*type0

Taiprotool'> =ow so*f! is t(e so*et $le !esriptor0 si"ilar to a $le

Client connect&so*f!0 res)Taia!!r0 res)Taia!!rlen'>

(is will onnet to t(e re"ote a!!ress www/e%a"ple/

in res)Taia!!r an! on port 3.MA


S S * t


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Server So*et

geta!!rinfo&4www/e%a"ple/o"5 05(ttp50 Q(ints0 Qres'>

so*f! N so*et&res)Taifa"ily0 res)Taiso*type0 res)Tai =ow so*f! is t(e so*et $le !esriptor0 si"ilar to a $le !esripto

Server7 (ints/aiags N -+SS-JE> ;; use loal a!!ress

geta!!rinfo&=ULL0 3.MA0 Q(ints0 Qres'>

so*etf! N so*et&res)Taifa"ily0 res)Taiso*type0 res)Taiprot

bin!&int so*f!0 res)Taia!!r0 res)Taia!!rlen'> Bin!s so*f! !ata struture to t(e loal -+ a!!ress an! port 3.MA

so*f! N so*et $le !esriptor

res)Taia!!r N pointer to a!!ress infor"ation2 port nu"ber

res)Taia!!rlen N lengt( in bytes of t(e a!!ress

Server an now listenon so*f!

G(en it (as a reuest0 it an accept


lilisten& ' for


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Client)Server


Client +roess&Server'

onnet& 'port .AAA

o*ay

listen& ' foronnetionreuests atport .AAA

+roessis busy

Client

onnet& 'port .AAA

Client+roess&Server'

o*ay

Client

onnet& 'port .AAA

C(il!new port 6A9M

new so*f!

port 6A9M +roessis not busy

accept( )

S * t


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So*ets Client will onnet to a server

onnet&so*f!0 res)Taia!!r0 res)Taia!!rlen'>

(is will onnet to t(e re"ote -+ a!!ress spei$e! in res)Tai+ort fro" so*f!

Server waits;listens for onnetions fro" lients int listen&int so*f!0 int ba*log'>

Calls &onnetion reuests' arrive at t(e server an! are ueuet(ey are 4aepte!5

ba*log N "a%i"u" nu"ber ino"ing alls in a ueue -t listens on a port0 say port 1,3.

int aept&int so*f!0 struta!!r


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So*ets sen!&int so*f!0 onst voi!


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Client Server

Client ServerCreate so*etConnect

Create solistenCall ueue

accept

Ket a newCreate a to use

sen!rev


-!eas


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-!eas

Brea* up t(e progra""ing proble" into s"aller (un*s so ttest it

E%a"ple2 art 12 Use t(e lient server progra"s fro" BeePs gui!e/ #un t(e" to "a*

wor* art 22 Io!ify t(e server so t(at it e%eutes 4ls5 every ti"e it gets a onne

fro" t(e lient/ =ote t(e output of 4ls5 goes to t(e onsole of t(e server/ (ter"inates t(e onnetion/

(is will give you e%periene wit( e%el an! proesses &an! also "aybe pipes'

art 2 Io!ify t(e server so t(at it e%eutes 4ls5 every ti"e it gets a onnefro" t(e lient but t(e output of 4ls5 goes t(roug( t(e so*et ba* to t(e liwill ter"inate t(e onnetion/ (e lient will !isplay t(e output

(is will give you e%periene wit( pipes as well as so*ets

art 2 Io!ify t(e lient so t(at it aepts t(e t(ree o""an!s &4list50 4(eW$lena"eT50 an! 4get W$lena"eT5' fro" t(e user0 starts a onnetion persen!s a "essage to in!iate t(e o""an! to t(e server &e/g/0 4list50 4(e*4get W$le na"eT5'/ (e server is "o!i$e! so t(at it aepts t(e onnetiono""an! on its own onsole0 e%eutes ls0 sen!s t(e output of ls ba* to t(e

art 32 Co"plete t(e proPet


-!eas


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-!eas

Hint2 Io!el2 lient sen!s reuest )T server proess replies

Have ea( transation orrespon! to a new onnet0 i/ter"inate a onnetion after a reply


Documents

Linux Client-Server Overview