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1、http头信息详解HTTP(HyperTextTransferProtocol)istheabbreviationofhypertexttransferprotocol,whichisusedtotransmitdatainWWWmode・PleaserefertoRFC2616formoredetailsaboutHTTPprotoco1.TheHTTPprotocolusesarequest/responsemodel・Thedientsendsarequesttotheserver,therequestheadertoincludetherequest,theURI,thep
2、rotocolversion,andtheMIMElikemessagestructurethatcontainstherequestmodifier,thecustomerinformation,andthecontent.Theserveractsasaresponsetoastatusline,includingtheversionofthemessageprotocol,successorerrorencoding,plusserverinfomiation,entitymetainformation,andpossibleentitycontent.Typically,t
3、heHTTPmessageincludestheclient，srequestmessagetotheserverandtheserver，sresponsemessagetothedient.Thesetwotypesofmessagesconsistofastartline,oneormoreheaderdomains,ablanklinethatisonlytheendoftheheaderdomain,andanoptionalmessagebody.TheheaderfieldoftheHTTPconsistsoffourparts:auniversalheader,ar
4、equestheader,aresponseheader,andanentityhead.Eachheaderfieldconsistsofthreeparts,adomainname,acolon(and),andadomainvalue・Thedomainnameiscaseinsensitive,andanynumberofwhitespacecharacterscanbeaddedbeforethedomainvalue.Theheaderfieldcanbeextendedtomultiplelines,andatleastonespaceortabisusedatthe
5、beginningofeachline.UniversalheaderfieldThegenericheaderfieldcontainstheheaderdomainssupportedbybothrequestandresponsemessages,andtheuniversalheaderdomainscontainCache-Control,Connection,Date,Pragma,Transfer-Encoding,Upgrade,andVia・Extensionstotheuniversalheaddomainrequirethatbothsidesofthecom
6、municationsupportthisextension,andthatifthereisanunsupportedgenericheaderdomain,itwillgenerallybetreatedasanentityheaderdomain.HereareafewsimplegeneralheaderdomainsthatareusedinUPnPmessages・Cache-ControlheaderfieldCache-Controlspecifiesthecachingmechanismfollowedbytherequestandresponse・Setting
7、uptheCache-Controlintherequestmessageorresponsemessagedoesnotmodifythecachehandlingprocessinanothermessageprocessing・Whentheinstructioncacherequestsincludingno-cache,no-store,max-age,max-stale,min-fresh,only-if-cached,theresponsemessage
