網(wǎng)絡(luò)編程2013寫一個簡單客戶端服務(wù)器端交互程序

NetworkIntroductiontoComputerSystems24thLecture,Dec.12,2013XiangqunChen，JunlinLuReviewof ,connection,portRevisitof -serverSocketinterface,EchosideServersideTestofEchoAProgrammer’sViewoftheHostsaremappedtoasetof32-bitIPThesetofIPaddressesismappedtoasetofidentifierscalledInte names79ismappedAprocessononeInte hostcancommunicatewithaprocessonanotherInte hostoveraconnection AsocketisanendpointofaAportisa16-bitintegerthatidentifiesaEphemeralport:AssignedautomaticallyandtemporarilyonwhenmakesaconnectionrequestWell-knownport:port80isassociatedwithWebAconnectionisuniquelyidentifiedbythesocketaddressesofidpoints(socketpair)(cliaddr:cliport,PuttingitallAnatomyofan socketaddress

Serversockethostaddress

51213isanephemeralportallocatedbythekernel

80isawell-knownportReviewof ,connection,portRevisitof -serverSocketinterface,EchosideServersideTestofEcho -Server sends4.

sends Note:sandserversareprocessesrunningonhosts(canbethesameordifferenthosts) workapplicationsarebasedonthe-serverServerhandlerequestforresourcesExamplesofWebbrowsers, net,Howdoes findtheserver?IPaddr:portTheIPaddressintheserversocket entifiesthe(moreprecisely,anadapterontheThe(well-known)portintheserversocketaddre entifiestheservice,andthusimplicitlyidentifiestheserverprocessthatperformsthatservice.ExamplesofwellknowPort7:EchoPort23:netPort25:MailPort80:WebUsingPortstoIdentifyServerhosthost

(i.e.,theWeb

(port80)(port7)(i.e.,theecho(portEcho(port Serversarelong-runningprocesses(daemons程序Createdatboot-time(typically)bytheinitprocess(processRuncontinuouslyuntilthemachineisturnedEachserverwaitsforrequeststoarriveonawell-knownportassociatedwithaparticularservicePort7:echoPort netPort25:mailPort80:HTTPAmachhatrunsaserverprocessisalsooftenreferredasaServerWebserver(portResource:files/computecycles(CGIService:retrievesfilesandrunsCGIprogramsonbehalfofSee/etc/servicesforacomprehensivelistofSee/etc/servicesforacomprehensivelistoftheport sonaLinuxResource:Service:storesandretrievenetserverResource:Service:proxiesaterminalontheserverMailserver “spool”Service:storesmailmessagesinspoolReviewof ,connection,portRevisitof -serverSocketinterface,EchosideServersideTestofEchoSocketsCreatedintheearly80’saspartoftheoriginalBerkeleydistributionofUnixthatcontainedanearlyversionofthe Providesauser-levelinterfaceto Underlyingbasisforall Basedon/serverprogrammingsocket Connect(IPaddr,port

Whatisa

Tothekernel,asocketisanendpointofToanapplication,asocketisafiledescriptorthatletstheapplicationread/writefrom/toth wrRemember:AllUnixI/Odevices,ludinworks,modeledas sandserverscommunicatewitheachotherbyreadingfromandwritingtosocketdescriptorsThemaindisttionbetweenregularfileI/OandsocketI/Oishowtheapplication“opens”thesocketdescriptorsOverviewoftheSockets Server打開 發(fā) 等/

requestfromnextSocketAddressGenericsocketForaddressargumentstoconnect,bind,andNecessaryonlybecauseCdidnothavegeneric(void*)pointerswhenthesocketsinterfacewasdesignedstructstruct{short/*protocolfamily/*addressSocketAddress -specificsocketMustcast(sockaddr_in*)to(sockaddr*)forconnect,bind,andacceptstructstructsockaddr_inunsignedshortunsignedshortstructin_addrunsignedchar/*addressfamily(always)/*portnum/*IPaddrworkbyteorderworkbyteorder*/sin_zero[8];/*padtosizeof(structsockaddr)*/ 00000000Example:Echoandgreatwhite>./echoserverigreatwhite>./echoserverilinux>serverconnectedserverconnectedtoBRYANT-TP4.VLSI.CS.CMU.EDU(9),port64690oserverreceived12type:OConnectionReviewof ,connection,portRevisitof -serverSocketinterface,EchosideServersideTestofEcho

EchoMain lude/*usage:./echo hostport*/intmain(intargc,char**argv){ fd,char*host,buf[MAXLINE];rio_trio;host=argv[1];port=fd=Open_fd(host,

Sendlo

printf("type:");while(Fgets(buf,MAXLINE,stdin)!=NULL) fd,buf,from Rio_readlineb(&rio,buf,Fputs(buf,stdout);printf("type:");

} Connect在 fd函數(shù) OverviewoftheSockets Server

:open_int fd(char*hostname,int{int structhostent*hp;structsockaddr_in

Thisfunctionopensaconnectionfromthetotheserveratif(( fd=socket(AF_ ,SOCK_STREAM,0))<0)return-1;/*checkerrnoforcauseoferror*//*Fillintheserver'sIPaddressandportif((hp=gethostbyname(hostname))==return-2;/*checkh_errnoforcauseoferror*/bzero((char*)&serveraddr,sizeof(serveraddr));serveraddr.sin_family=AF_ bcopy((char*)hp-(char*)&serveraddr.sin_addr.s_addr,hp->h_length);serveraddr.sin_port=htons(port);/*Establishaconnectionwiththeserver*/if(connect( fd,(SA*)&serveraddr,sizeof(serveraddr))<return-1; }

:open_socketcreatesasocketdescriptoronJustallocates&initializessomeinternaldata :indicatesthatthesocketisassociatedwith SOCK_STREAM:selectsareliablebytestreamfd;/*socketdescriptorif<fd=,SOCK_STREAM,return-1;/*checkerrnoforcauseoferror... :open_Thethenbuildstheserver’s /*socketdescriptorstructhostent*hp; /*DNShostentry*/structsockaddr_inserveraddr;/*server’sIPaddress*//*fillintheserver'sIPaddressandport*/if((hp=gethostbyname(hostname))==NULL)return-2;/*checkh_errnoforcauseoferror*/bzero((char*)&serveraddr,sizeof(serveraddr));serveraddr.sin_family=AF_ serveraddr.sin_port=htons(port);bcopy((char*)hp-

ACarefulLookatbcopy/*DNShostentrystructure*/structhostent{.. /*lengthofanaddress,inbytes*/ **h_addr_list;/*null-terminatedarrayofin_addrstructsstructsockaddr_in..structin_addr /*IPaddriworkbyte./*Inteaddressstructure*/structin_addr{unsignedints_addr;workbyteorder(big-endian)structstructhostent/*DNShostentrystructsockaddr_inserveraddr;/*server’ssocketaddressbcopy((char*)hp->h_addr_list[0],/*src,dest(char*)&serveraddr.sin_addr.s_addr,hp-BcopyArgumentDatastruct ..0 struct0000000000000tructs :open_Finallythecreatesaconnectionwiththeprocesssuspends(blocks)untiltheconnectionisAfterresuming,the isreadytobeginexchangingmessageswiththeserverviaUnixI/Ocallsondescriptor /*socketdescriptor*/structsockaddr_inserveraddr; /*serveraddress*/typedefstructsockaddrSA; /*genericsockaddr*//*Establishaconnectionwiththeserverif fd,(SA*)&serveraddr,sizeof(serveraddr))return-1; }Reviewof ,connection,portRevisitofa-serverSocketinterface,EchosideServersideTestofEcho

EchoServer:Mainintmain(intargc,char**argv)intlistenfd,connfd,port, structsockaddr_ structhostent*hp;char*haddrp;unsigned port=atoi(argv[1]);/*theserverlistensonaportonthecommandlinelistenfd=while(1)len= connfd=Accept(listenfd,(SA*)& addr,& hp=Gethostbyaddr((constchar*)& addr.sin_addr.s_addr),AF_ haddrp= _port=ntohs( printf("serverconnectedto%s(%s),port%u\n",hp->h_name, }}OverviewoftheSockets

Officeephoneogyfor Buya lthelocaladministratorwhatnumberyouwanttouse Plugthephone Answerthephonewhenitrings=EchoServer:intopen_listenfd(int{intlistenfd,optval=1;structsockaddr_inserveraddr;/*/*Createasocketdescriptorif((listenfd=socket(AF_return-1;,0))</*Eliminates"Addressalreadyinuse"errorfrombind.*/if(setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,(constvoid*)&optval,sizeof(int))<return-...EchoServer:open_listenfd/*ListenfdwillbeanendpointforallrequeststoportonanyIPaddressforthishost*/bzero((char*)&serveraddr,sizeof(serveraddr));serveraddr.sin_family=AF_ serveraddr.sin_addr.s_addr=htonl(INADDR_ANY);serveraddr.sin_port=htons((unsignedshort)port);if(bind(listenfd,(SA*)&serveraddr,sizeof(serveraddr))return-/*Makeitalisteningsocketreadytoacceptconnectionrequests*/if(listen(listenfd,LISTENQ)<0)return-1;return}EchoServer:socketcreatesasocketdescriptoronthe :indicatesthatthesocketisassociatedwith SOCK_STREAM:selectsareliablebytestreamconnectionintintlistenfd;/*listeningsocketdescriptor/*Createasocketdescriptorif((listenfd=socket(AF_ ,SOCK_STREAM,0))<0)return-1;EchoServer:Thesocketcanbegivensome/*Eliminates"Addressalreadyinuse"errorfrombind().*/if(setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,(constvoid*)&optval,sizeof(int))<return- HandytrickthatallowsustoreruntheserverimmediayafterwekillitOtherwisewewouldhavetowaitabout15Eliminates“Addressalreadyinuse”errorfromStronglysuggestyoudothisforallyourserverstosimplifyEchoServer:(initializesocketInitializesocketwithserverportAcceptconnectionfromanyIPstructstructsockaddr_inserveraddr;/*server'ssocketaddr/*listenfdwillbeanendpointforallrequeststoportonanyIPaddressforthishost*/bzero((char*)&serveraddr,sizeof(serveraddr));serveraddr.sin_family=AF_ serveraddr.sin_port=htons((unsignedshort)port);serveraddr.sin_addr.s_addr=htonl(INADDR_ANY);IPaddrandportstored work(big-endian)byte ADD00000000

EchoServer:bindassociatesthesocketwiththesocketaddresswejustintlistenfd; /*listeningsocket*/structintlistenfd; /*listeningsocket*/structsockaddr_inserveraddr;/*server’ssocketaddr*//*listenfdwillbeanendpointforallrequeststoportonanyIPaddressforthishost*/if(bind(listenfd,(SA*)&serveraddr,sizeof(serveraddr))<0)return-1;EchoServer:listenindicatesthatthissocketwillacceptconnection(connect)requestsfrom LISTENQisconst dicatinghowmanypendingrequestsintintlistenfd;/*listeningsocket/*Makeitalisteningsocketreadytoacceptconnectionrequests*/if(listen(listenfd,LISTENQ)<0)return-1;returnlistenfd;}We’refinallyreadytoenterthemainserverloopthatacceptsandprocessesconnectionrequests.EchoServer:MainTheserverloopsendlessly,waitingforconnectionrequests,thenreadinginputfromthe,andechoingtheinputbacktothe.main()/*createandconfigurethelisteningsocket*/準備工作就緒：socket,open_listenfd,bindaddress+port#while(1){}Accept():waitforaconnectionrequestecho():readandechoinputlinesfrom tilEOF*/Close():closetheconnection*/}OverviewoftheSockets Server /

requestfromnextEchoServer:accept()blockswaitingforaconnectionintintlistenfd;/*listeningdescriptor*/intconnfd;/*connecteddescriptor*/structsockaddr_lientaddr;intlen=connfd=Accept(listenfd,(SA acceptreturnsaconnecteddescriptor(connfd)withthesamepropertiesasthelisteningdescriptorReturnswhentheconnectionbetweenandserveriscreatedandreadyforI/OtransfersAllI/Owiththewillbedoneviatheconnectedacceptalso lient’sIPEchoServer:accept

Serverblocksinaccept,waitingforconnectionrequestonlisteningdescriptor

makesconnectionrequestbycallingandblocking connfdServerreturnsconnfd returnsfromConnectionisnowestablishedfdandConnectedvs.ListeningListeningdescriptor一直存在=服務(wù)器時Endpoint CreatedonceandexistsforlifetimeoftheEndpointoftheconnection andAnewdescriptoriscreatedeachtimetheserveracceptsaconnectionrequestfromaExistsonlyaslongasittakestoWhythe tion?AllowsforconcurrentserversthatcancommunicateoversimultaneouslyE.g.,Eachtimewereceiveanewrequest,weforkachildtohandletherequestEchoServer:IdentifyingtheTheservercandetermhename,IPaddress,andportofthestructhost