PDF-1 - Tomas Vitvar

Transcription

MiddlewareandWebServices
Lecture3:ApplicationProtocols
doc.Ing.TomášVitvar,Ph.D.
tomas@vitvar.com•@TomasVitvar•http://vitvar.com
CzechTechnicalUniversityinPrague
FacultyofInformationTechnologies•SoftwareandWebEngineering•http://vitvar.com/courses/mdw
Modified:TueSep152015,19:58:18
Humlav0.3
Overview
IntroductiontoApplicationProtocols
‒SynchronousandAsynchronousCommunication
‒SelectedNetworkingConcepts
SimpleProtocolExample
IntroductiontoHTTP
Lecture3:ApplicationProtocols,CTUWinterSemester2014/2015,@TomasVitvar
‒2‒
ApplicationProtocols
Rememberthis
AppprotocolsmostlyontopoftheTCPLayer
‒useTCPsocketforcommunication
Majorprotocols
‒HTTP–mostoftheappprotocolslayeredonHTTP
→widespread,but:implementorsoftenbreakHTTPsemantics
‒RMI–RemoteMethodInvocation
→Java-specific,ratherinterface
→mayuseHTTPunderneath(amongotherthings)
‒XML-RPC–RemoteProcedureCallandSOAP
→Again,HTTPunderneath
‒WebSocket–newprotocolpartofHTML5
‒3‒
Socket
Handshaking(connectionestablishment)
‒Theserverlistensat[dst_ip,dsp_port]
‒Three-wayhandshake:
→theclientat[src_ip,src_port]sendsaconnectionrequest
→theserverresponds
→theclientacknowledgestheresponse,cansenddataalong
‒Resultisasocket(virtualcommunicationchannel)withuniqueidentification:
socket=[src_ip,src_port;dst_ip,dst_port]
Datatransfer(resourceusage)
‒Client/serverwrites/readsdatato/fromthesocket
‒TCPfeatures:reliabledelivery,correctorderofpackets,flowcontrol
Connectionclose
‒4‒
AddressinginApplicationProtocol
IPaddressing:IPisanaddressofamachineinterface
‒Amachinecanhavemultipleinterfaces(eth0,eth1,bond0,...)
TCPaddressing:TCPportisanaddressofanapprunningonamachine
andlisteningonamachineinterface
‒MultipleapplicationswithdifferentTCPportsmaylistenonamachineinterface
Applicationaddressing
‒Additionalmechanismstoaddressentitieswithinanapplication
‒TheyareoutofscopeofIP/TCP,theyareappspecific
→forexample,WebappsservedbyasingleWebserver
‒5‒
VirtualIP
VirtualIP
‒AdditionalIPaddressesassignedtoanetworkinterface
→Forexample,eth0–eth0:1,eth0:2,eth0:3,...
→AprocesscanbindtothevirtualIP
→MultipleprocessescanlistenonthesametcpportbutondifferentvirtualIPs
Benefits
‒FloatingIP–aprocesscanmovetransparentlytoanotherphysicalmachine
‒Networkconfigurationcanbepreserved,noneedtoreconfigure
‒FailoverconceptusesfloatingIPs
‒6‒
VirtualIPConfiguration
StepstoconfigurevirtualIPinLinux(exampleforeth0)
1. Findouttheinterface'snetworkmask
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$ifconfigeth0
eth0Linkencap:EthernetHWaddr00:0C:29:AB:5E:6A
inetaddr:172.16.169.184Bcast:172.16.169.255Mask:255.255.255.0
...
2. CreatevirtualIPusingifconfig
‒itshouldusethesamenetworkmask
‒itshouldbefree,usuallyallocatedtobeusedasavirtualIP
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$sudoifconfigeth0:1172.16.169.184netmask255.255.255.0
$ifconfigeth0:1
eth0:1Linkencap:EthernetHWaddr00:0C:29:AB:5E:6A
inetaddr:172.16.169.186Bcast:172.16.169.255Mask:255.255.255.0
3. Updateneighbours'ARP(AddressResolutionProtocol)caches
‒toassociatethevirtualIPwithMACaddressofeth0
‒whenthevirtualIPwasinuseonothernodeorinterface
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$sudoarping-q-U-c3-Ieht0172.16.169.184
Tasks
‒ConfigureavirtualIPonyourcomputerandtestitusingping
‒7‒
Overview
IntroductiontoHTTP
‒8‒
SynchronousandAsynchronousCommunication
Synchronous
‒onesocket,|treq–tres|issmall
‒easytoimplementanddeploy,onlystandardfirewallconfig
‒onlytheserverdefinesendpoint
Asynchronous
‒request,responseeachhassocket,clientandserverdefineendpoints
‒|treq–tres|canbelarge(hours,evendays)
‒hardertodoacrossnetworkelements(private/publicnetworksissue)
‒9‒
AsynchronousviaIntermediary
Intermediary
‒Acomponentthatdecouplesaclient-servercommunication
‒Itincreasesreliabilityandperformance
→Theservermaynotbeavailablewhenaclientsendsarequest
→Therecanbemultipleserversthatcanhandletherequest
FurtherConcepts
‒MessageQueues(MQ)–queue-basedcommunication
‒Publish/Subscribe(P/S)–event-drivencommunication
‒10‒
AsynchronousviaPolling
Polling–onlyclientsopensockets
‒Aclientperformsmultiplerequest-responseinteractions
→Thefirstinteractioninitiatesaprocessontheserver
→Subsequentinteractionscheckfortheprocessingstatus
→Thelastinteractionretrievestheprocessingresult
Propertiesofenvironments
‒Aservercannotopenasocketwiththeclient(networkrestrictions)
‒TypicallyontheWeb(aclientrunsinabrowser)
‒11‒
Overview
IntroductiontoHTTP
‒12‒
Public/PrivateNetworkConfiguration
Addscomplexitytoconfigurationofapplication
‒Configexampleatserverwitheth0=147.32.100.1(iptables)
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#enableipforwardingfromoneinterfacetoanotherwithinlinuxcore
echo1>/proc/sys/net/ipv4/ip_forward
#redirectallcommunicationcomingtotcp/3000to192.168.1.2:4000
iptables-tnat-APREROUTING-ieth0-ptcp--dport3000-jDNAT\
--to-dest192.168.1.2--to-port4000
‒13‒
DemilitarizedZones
DMZ=DemilitarizedZone
‒subnetwithinanorganization'snetworkonapublicnetwork
‒specialcareofsecurityenforcedthroughinternalpolicies
‒Forexample:
→noaccesstoalllivedata,subsetscopiedinbatches
→frequentmonitoring
‒14‒
VirtualPrivateNetwork
VPN=VirtualPrivateNetwork
‒anoverlaynetworkbetweenaclientandaserver
‒thenetworkspansaccrossunderlyingnetworkelements
‒Example:
→VPNclientstartsaVPNconnectionwiththeVPNservervianetworkinterfaces
→VPNserverassignsanIPaddresstotheVPNclientfromtheserver'ssubnet
→PacketsinVPNcommunicationareencryptedandsentoutinanouterVPN
packet,e.g.IPSecpacket
‒15‒
ProxyServer
ProxyServer
‒Centralizedaccesscontrolbasedoncontent
‒Perfomsrequestonbehalfoftheclient
→Cachescontenttoincreaseperformance,limitsnetworktraffic
→Filtersrequestsbasedontheirdestinations
‒Widelyusedinprivatenetworksincompanies
‒MostoftheproxyserverstodayareWebproxyservers
‒16‒
ReverseProxyServer
ReverseProxyServer
‒Aggregatesmultiplerequest-responseinteractionswithback-endsystems
‒Processestherequestonbehalfoftheclient
‒Providesadditionalvaluestocommunication
→Datatransformations
→Security–authentication,authorization
→Orchestrationofcommunicationwithback-endsystems
‒Examples:EnterpriseServiceBus,SecurityGateway
‒17‒
Overview
IntroductiontoHTTP
‒18‒
TCPSocketProtocol
ExamplesimpleTCPSocketprotocolinJava
‒functions(verbs):addandbye
‒datasyntax:add"^[0-9]+[0-9]+$",bye"^$"(regulargrammars)
‒datasemantics:adddecimalnumbers,byenone
‒process:transitionsS1—add—S1,S1—bye—S0,whereS0,S1arestatessuchthat
S1=connectionestablished,S0=connectionclosed.
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packagecom.vitvar.ctu.mdw;
importjava.io.*;
importjava.net.*;
importjava.util.regex.*;
/**
*Simpleprotocolexample.Theclassstartsalistenerontheport8080.
*Whenaclientconnects,theserverparsestheinputinaform"addab",
*where"a"and"b"areintegervalues,addsthetwonumbersandsends
*theresultbacktotheclient.Thecommunicationendswhentheclientsends"bye".
*
*@authortomas@vitvar.com
*
*/
publicclassSimpleProtocol{
publicstaticvoidmain(String[]args)throwsIOException{
//infomessagetotheconsole
System.out.println("Listeningonport8080...");
‒19‒
TCPSocketProtocol(Cont.)
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//listenonport8080
ServerSocketserverSocket=newServerSocket(8080);
SocketclientSocket=serverSocket.accept();
//createreaderandwritertoreadfromandwritetothesocket
PrintWriterout=newPrintWriter(clientSocket.getOutputStream(),true);
BufferedReaderin=newBufferedReader(
newInputStreamReader(clientSocket.getInputStream()));
//printinformationtotheclient
out.println("verbs:addab,bye");
//grammardefinition
Patternp=Pattern.compile("^add([0-9]+)([0-9]+)$");
Matcherm;Stringmessage;
//readinputfromtheclientandprocesstheinput
while((message=in.readLine())!=null){
if((m=p.matcher(message)).matches())
out.println("Result:"+(Integer.parseInt(m.group(1))+
Integer.parseInt(m.group(2))));
else
if(message.equals("bye")){
out.println("Goodbye!");
break;
}else
out.println("Donotunderstand:"+message);
}
}
}
‒20‒
Testing
Manyappprotocolscommunicateinplaintext
‒messagesinASCIIorBase64encoded(printablecharsonly)
‒thisallowstotestthemjustwithTelnet
→Telnetdoesnotknowaboutanyprotocol-specificsemantics
→onlyopens,reads/writes,andclosesthesocket
Testingourprotocol
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#1.runthelistener
bin/simple_protocol.sh
Listeningonport8080...
#2.openthesocketusingtelnetbutfirstdigforDNSlookup
telnet127.0.0.18080
Trying127.0.0.1...
Connectedtolocalhost.
Escapecharacteris'^]'.
Verbs:addab,bye.
add34
Theresultis:7
minus75
Donotunderstand:minus75
bye
Goodbye!
‒21‒
Overview
IntroductiontoHTTP
‒StateManagement
‒22‒
HypertextTransferProtocol–HTTP
Applicationprotocol,basisofWebarchitecture
‒PartofHTTP,URI,andHTMLfamily
‒Request-responseprotocol
Onesocketforsinglerequest-response
‒originalspecification
‒havechangedduetoperformanceissues
→manyconcurrentrequests
→overheadwhenestablishingsameconnections
→HTTP1.1offerspersistentconnectionandpipelining
HTTPisstateless
‒MultipleHTTPrequestscannotbenormallyrelatedattheserver
→"problems"withstatemanagement
→RESTgoesbacktotheoriginalHTTPidea
‒23‒
HTTPRequestandResponse
RequestSyntax
methodurihttp-version<crlf>
(header:value<crlf>)*
<crlf>
[data]
ResponseSyntax
http-versionresponse-code[message]<crlf>
(header:value<crlf>)*
<crlf>
[data]
Semanticsofterms
method="GET"|"POST"|"DELETE"|"PUT"|"HEAD"|"OPTIONS"
uri=[path][";"params]["?"query]
http-version="HTTP/1.0"|"HTTP/1.1"
response-code=validresponsecode
header:value=validHTTPheaderanditsvalue
data=resourcestaterepresentation(hypertext)
‒24‒
ServingHTTPRequest
IPandTCPaddressing
1. UserentersURLhttp://company.cz:8080/orderstothebrowser
2. BrowsergetsanIPaddressforcompany.cz,IP:138.232.189.127
3. BrowserandWebServercreatesasocket
[147.32.100.5:3223;138.232.189.127:8080]
Applicationaddressing
4. BrowsersendsHTTPrequest,thatis,writesfollowingdatatothesocket
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GET/ordersHTTP/1.1
Host:company.cz
5. Webserverpassestherequesttothewebapplicationcompany.czwhichserves
GETordersandthatwritesaresponsebacktothesocket.
‒25‒
HTTPListener
HTTPlistenerimplementationinJavausingJetty
‒Serverlistensonport8080
‒JettyparsesHTTPrequestdataintoHttpServletRequestobject.
‒Whenaclientconnects,themethodhandleRequestiscalled
‒Themethodteststhevalueofthehostheaderandrespondsbackifthe
headermatchescompany.czvalue.
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/**handlestherequestwhenclientconnects**/
publicvoidhandleRequest(HttpServletRequestrequest,
HttpServletResponseresponse)throwsIOException,ServletException{
//testifthehostiscompany.cz
if(request.getHeader("Host").equals("company.cz")){
response.setStatus(200);
response.setHeader("Content-Type","text/plain");
response.getWriter().write("Thisistheresponse");
response.flushBuffer();
}else
response.sendError(400);//badrequest
}
‒26‒
HTTPListener(Cont.)
TestitusingTelnet
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telnet127.0.0.18080
#...linesomittedduetobrevity
GET/ordersHTTP/1.1
Host:company.cz
HTTP/1.1201OK
Content-Type:plain/text
Thisistheresponse...
HTTPlistenerinbash
‒UseittotestincommingHTTPconnectionsquickly
‒Usesncutility(netcat)
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#ctrl-ctostophttplistener
control_c(){
echo-en"\n*Exiting\n"
exit$?
}
trapcontrol_cSIGINT
for((;;))
do
echo-e"\n\n*Listeningonport$1..."
echo-e"\nHTTP/1.0204NoContent\n\n"|nc-l$port
done
‒27‒
VirtualWebServer
Virtualserver
‒Configurationofanamedvirtualwebserver
‒Webserveruseshostrequestheadertodistinguishamongmultiplevirtual
webserversonasinglephysicalhost.
ApachevirtualWebserverconfiguration
‒Twovirtualservershostedonasinglephysicalhost
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#allIPaddresseswillbeusedfornamedvirtualhosts
NameVirtualHost*:80
<VirtualHost*:80>
ServerNamecompany.com
ServerAdminadmin@company.com
DocumentRoot/var/www/apache/company.com
</VirtualHost>
<VirtualHost*:80>
ServerNamefirm.cz
ServerAdminadmin@firm.cz
DocumentRoot/var/www/apache/firm.cz
</VirtualHost>
‒28‒
BetterSupportforHTTPTesting
UsecurltotestHTTPprotocol
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Usage:curl[options...]<url>
-X/--request<command>Specifyrequestcommandtouse
-H/--header<line>Customheadertopasstoserver
-d/--data<data>HTTPPOSTdata
-b/--cookie<name=string/file>Cookiestringorfiletoreadcookiesfrom
-v/--verboseMaketheoperationmoretalkative
Example
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curl-v-H"Host:company.cz"127.0.0.1:8080
*Abouttoconnect()to127.0.0.1port8080
*Trying127.0.0.1...connected
*Connectedto127.0.0.1port8080
>GET/HTTP/1.1
>User-Agent:curl/7.20.0(i386-apple-darwin10.3.2)libcurl/7.20.0OpenSSL/0.9.8n
>Accept:*/*
>Host:company.cz
>
<HTTP/1.1201OK
<Connection:keep-alive
<Content-Type:plain/text
<
<Thisistheresponse...
‒29‒
Overview
IntroductiontoHTTP
‒StateManagement
‒30‒
StateManagement
HTTPisastatelessprotocol–originaldesign
‒Noinformationtorelatemultipleinteractionsatserver-side
→ExceptAuthorizationheaderiscopiedineveryrequest
→IPaddressesdonotwork,onepublicIPcanbesharedby
multipleclients
Solutionstocheckforavalidstateatserver-side
‒Cookies–obviousandthemostcommonworkaround
→RFC2109–HTTPStateManagementMechanism
→Allowclientsandserverstotalkinacontextcalledsessions
‒Hypertext–originalHTTPdesignprinciple
→Appstatesrepresentedbyresources(hypermedia),linksdefine
transitionsbetweenstates
→AdoptedbytheRESTprinciplestatelessness
‒31‒
InteractionwithCookies
Request-responseinteractionwithcookies
‒Sessionisalogicalchannelmaintainedbytheserver
StatefulServer
‒Serverremembersthesessioninformationinaservermemory
‒Servermemoryisanon-persistentstorage,whenserverrestarts
thememorycontentislost!
‒32‒
Set-CookieandCookieHeaders
Set-Cookieresponseheader
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set-cookie="Set-Cookie:"cookie(","cookie)*
cookie=NAME"="VALUE(";"cookie-av)*
cookie-av="Comment""="value
|"Domain""="value
|"Max-Age""="value
|"Path""="value
‒domain–adomainforwhichthecookieisapplied
‒Max-Age–numberofsecondsthecookieisvalid
‒Path–URLpathforwhichthecookieisapplied
Cookierequestheader.Aclientsendsthecookieinarequestif:
‒domainmatchestheoriginserver'sfully-qualifiedhostname
‒pathmatchesaprefixoftherequest-URI
‒Max-Agehasnotexpired
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cookie="Cookie:"cookie-value(";"cookie-value)*
cookie-value=NAME"="VALUE[";"path][";"domain]
path="$Path""="value
domain="$Domain""="value
‒domain,andpatharevaluesfromcorrespondingattributesoftheSet-Cookie
header
‒33‒
SessionManagementJavaClass
Managesclientsessionsinaservermemory
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publicclassSessions<E>{
//storageforthesessiondata;
privateHashtable<String,E>sessions=newHashtable<String,E>();
/**Returnssessionidbasedontheinformationinthehttprequest**/
publicStringgetSessionID(HttpServletRequestrequest)throwsException{
Stringsid=null;
//extractthesessionidfromthecookie
if(request.getHeader("cookie")!=null){
Patternp=Pattern.compile(".*session-id=([a-zA-Z0-9]+).*");
Matcherm=p.matcher(request.getHeader("cookie"));
if(m.matches())sid=m.group(1);
}
//createthesessionidmd5hash;userandomnumbertogenerateaclient-id
//notethatthisisasimplesolutionbutnotveryreliable
if(sid==null||sessions.get(sid)==null){
MessageDigestmd=MessageDigest.getInstance("MD5");
md.update(newString(request.getRemoteAddr()+
Math.floor(Math.random()*1000)).getBytes());
sid=Utils.toHexString(md.digest());
}
returnsid;
}
publicEgetData(Stringsid)...//returnssessiondatafromsessionsobject
publicvoidsetData(Stringsid,Ed)...//setssessiondatatosessionsobject
}
‒34‒
StatefulServerImplementation
Simpleper-clientcounter
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publicvoidhandleRequest(HttpServletRequestrequest,
HttpServletResponseresponse)throwsException{
//getthesessionid
Stringsid=sessions.getSessionID(request);
//createthenewdataifnoneexists
if(sessions.getData(sid)!=null)
sessions.setData(sid,
Integer.valueOf(sessions.getData(sid).intValue()+1));
else
sessions.setData(sid,Integer.valueOf(1));
//sendtheresponse
response.setStatus(200);
response.setHeader("Set-Cookie","session-id="+sid+";MaxAge=3600");
response.setHeader("Content-Type","text/plain");
response.getWriter().write("Numberofhitsfromyou:"+
sessions.getData(sid).toString());
response.flushBuffer();
}
Task
‒Whathappenswhentheserverrestarts?
‒Howdoyouchangethecodetocountrequestsfromallclients?
‒35‒
Testing
Testing
‒curlwillrequireyoutospecifycookiesineveryrequest
‒Browserhandlescookiesautomatically
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#runcurlforthefirsttime
curl-v127.0.0.1:8080
>GET/HTTP/1.1
>Host:127.0.0.1:8080
>
<HTTP/1.1200OK
<Set-Cookie:session-id=3a9c3cdc5ff36434aa1ba860727ca401;max-age=3600
<
Numberofhitsfromyou:1
#copythecookiesession-idfrompreviousresponse
curl-v-bsession-id=3a9c3cdc5ff36434aa1ba860727ca401127.0.0.1:8080
>GET/HTTP/1.1
>Host:127.0.0.1:9900
>Cookie:session-id=3a9c3cdc5ff36434aa1ba860727ca401
>
<HTTP/1.1200OK
<Set-Cookie:session-id=3a9c3cdc5ff36434aa1ba860727ca401;max-age=3600
<
Numberofhitsfromyou:2
‒36‒

PDF-1 - Tomas Vitvar

Transcription

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