NI DataSocket Server Help - documentation.help · from National Instruments FieldPoint modules,...

NIDataSocketServerHelpApril2003Edition,PartNumber370716A-01UsethishelpfileasareferenceforinformationabouttheDataSocketServer,DataSocketServerManager,DataSocketServerDiagnosticsutility,andtheconceptsyouneedtounderstandsoyoucantransferdatausingtheDataSocketServer.Tonavigatethishelpfile,usetheContents,Index,andSearchtabstotheleftofthiswindow.Formoreinformationaboutthishelpfile,refertothefollowingtopics:Conventions—formattingandtypographicalconventionsinthishelpfileRelatedDocumentationImportantInformationTechnicalSupportResourcesTocommentonthedocumentation,emailtechpubs@ni.com©2003NationalInstrumentsCorporation.AllRightsReserved.

DataSocketServerOverviewADataSocketServerisanexecutablethatenablesdataexchangebetweenmultipleDataSocketReadersandDataSocketWriters.TheDataSocketServeracceptsandstoresinformationfromdatasourcesandrelaysittootherdatatargets.WhenyourunaDataSocketServeronacomputer,youmakedataeasilyaccessibletoDataSocketReadersandWritersonthesamecomputerorothercomputersconnectedthoughaTCPnetwork,suchastheInternet.

NoteTheDataSocketServerrequiressupportforTCP/IPnetworkingonthecomputer.IfyouhaveaworkingWebbrowseronthecomputer,theTCP/IPdriverisinstalled.

LaunchingtheDataSocketServerLaunchtheDataSocketServerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServer.

TipWhentheDataSocketServerisrunning,youseetheDataSocketiconintheWindowssystemtray,indicatingthattheDataSocketServerisrunning.Tocheckonitsstatus,right-clicktheDataSocketiconandselectShowDataSocketServerfromtheshortcutmenu.

ConfiguringtheDataSocketServerThedefaultDataSocketServerconfigurationworksformanyInternetapplications,butyoumightneedtochangetheconfigurationforsomeapplications.TomodifytheDataSocketServerconfiguration,usetheDataSocketServerManager.

NoteChangesthatyoumaketotheDataSocketServerusingtheDataSocketServerManagertakeeffectthenexttimeyoulaunchtheDataSocketServer.IfyouchangetheserverconfigurationintheDataSocketServerManagerwhentheDataSocketServerisrunning,youmustshutdownandlaunchtheDataSocketServeragainbeforethechangestakeeffect.

ShuttingDowntheDataSocketServerToshutdowntheDataSocketServer,selectServer»ShutdownDataSocketServerintheDataSocketServer.IftheDataSocketServerishidden,right-clicktheDataSocketiconintheWindowssystemtrayandselectShutdownDataSocketServerfromtheshortcutmenu.

DataItemsAdataitemonaDataSocketServerrepresentsareal-worldmeasurement.DataSocketReaderscansubscribetodataitemsonaDataSocketServer,andDataSocketWriterscancreateandpublishorupdatedataitemsonaDataSocketServer.Therearetwotypesofdataitems—predefineddataitemsanddynamicallycreateddataitems:

PredefineddataitemsalwaysexistontheDataSocketServer,andtheyalwayshaveaninitialvalueassociatedwiththem.BecausetheDataSocketServerneverreleasespredefineddataitems,theirvaluesexistevenwhennoDataSocketclientisconnectedtothem.Predefineddataitemscanhavespecialreadandwriteaccessgroupssoyoucanallowdifferentcomputerstoaccessdifferentpredefineddataitems.DynamicallycreateddataitemsexistonlyaslongasthereisatleastoneDataSocketclientconnectedtoreadorwritethedataitemvalue.Whennoconnectionstoadynamicallycreateddataitemremain,theDataSocketServerreleasesthedataitemanditsvalue.

Bydefault,onlyprogramsrunningonthesamecomputerastheDataSocketServercancreatedataitemsorpublishtodataitems,whereasapplicationsonthesamecomputerorothercomputerscanreaddataitems.UsetheDataSocketServerManagertospecifywhichcomputerscancreatedataitems,publishtodataitems,andsubscribetodataitems.

DataSourceAdatasourceisalocationtowhichyouwantaDataSocketReadertoconnectandretrievedata.YouspecifyadatasourcelocationwithaURL.LikeURLsyouuseinaWebbrowser,thedatasourcelocatorcanpointtomanydifferenttypesofsourcesdependingontheprefix.TheprefixiscalledtheURLscheme.DataSocketsupportsseveralschemes:

dstp:(DataSockettransferprotocol)http:(hypertexttransferprotocol)ftp:(filetransferprotocol)opc:(OLEforProcessControl)fieldpoint:,logos:,lookout:(communicationprotocolforNationalInstrumentsFieldPointmodules,NationalInstrumentsLabVIEWDataloggingandSupervisoryControl(DSC)Moduleprocesses,andNationalInstrumentsLookoutprocesses)file:(localfileservers)

DataTargetAdatatargetisalocationtowhichyouwantaDataSocketWritertoconnectandwritedata.YouspecifyadatatargetwithaURL.LikeURLsyouuseinaWebbrowser,thedatatargetlocatorcanpointtomanydifferenttypesofsourcesdependingontheprefix.TheprefixiscalledtheURLscheme.DataSocketsupportsseveralschemes:

dstp:(DataSockettransferprotocol)ftp:(filetransferprotocol)opc:(OLEforProcessControl)fieldpoint:,logos:,lookout:(communicationprotocolforNationalInstrumentsFieldPointmodules,NationalInstrumentsLabVIEWDataloggingandSupervisoryControl(DSC)Moduleprocesses,andNationalInstrumentsLookoutprocesses)file:(localfileservers)

DataSocketDataSocketisatechnologythatsimplifiesdataexchangebetweenanapplicationandotherapplications,files,FTPservers,andWebservers.ItprovidesonecommonAPItoanumberofdifferentcommunicationprotocols.DataSocket,bothatechnologyandagroupoftools,facilitatestheexchangeofdataandinformationbetweenanapplicationandanumberofdifferentdatasourcesanddatatargets.Thesesourcesandtargetsincludefiles,HTTP/FTPservers,OLEforProcessControl(OPC)servers,andNationalInstrumentsDataSocketServersforpublishinglivedatabetweenapplications.Often,thesesourcesandtargetsarelocatedonadifferentcomputer.YoucanspecifyDataSocketsourcesandtargets(connections)usingURLs(uniformresourcelocators)thatadheretothefamiliarURLmodel.DataSocketusesanenhanceddataformatforexchangingmeasurementdata,aswellastheattributesofthedata.Dataattributesmightincludeinformationsuchasanacquisitionrate,testoperatorname,timestamp,andqualityofdata.AlthoughyoucanusegeneralpurposefileI/Ofunctions,TCP/IPfunctions,andFTP/HTTPrequeststotransferdatabetweendifferentapplications,applicationsandfiles,anddifferentcomputers,youmustwriteasignificantamountofprogramcodetodoso.DataSocketgreatlysimplifiesthistaskbyprovidingaunifiedAPIfortheselow-levelcommunicationprotocols.TransferringdataacrosscomputerswithDataSocketisassimpleasusingabrowsertoreadWebpagesontheInternet.

DSTPDataSocketTransferProtocol.ProtocolbasedonTCP/IPthroughwhichdataispassedbetweenDataSocketclients—knownasDataSocketReaderandWriterapplications—usingtheDataSocketServer.YouconnecttoaDataSocketServerfromDataSocketReaderandWriterapplicationsusingtheDSTPURLscheme,asdemonstratedinthefollowingexampleURLs.ThefollowingURLconnectstothedataitemnamedwaveontheDataSocketServerrunningonthelocalcomputer:dstp://localhost/waveThefollowingURLconnectstothedataitemnamedwaveonaDataSocketServerrunningonanetworkedcomputernamedlab:dstp://lab/wave

LogosProtocolTheNationalInstrumentsLogosprotocolsendsandreceiveslivedatatoandfromNationalInstrumentsFieldPointmodules,NationalInstrumentsLabVIEWDataloggingandSupervisoryControl(DSC)Moduleprocesses,andNationalInstrumentsLookoutprocesses.ThefollowingURLsarefunctionallyequivalent:logos://computer_name/process/data_item_namelookout://computer_name/process/data_item_namefieldpoint://computer_name/process/data_item_name

DataSocketServerManagerTheDataSocketServerManagerisanexecutablethatconfiguresdefaultsettingsandpredefineddataitemsfortheDataSocketServeronthelocalcomputer.YoucanlaunchtheDataSocketServerManagerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServerManager.

NoteYoucannotconfigureaDataSocketServerremotelyorprogrammatically.YoumustlocallyconfiguretheDataSocketServerwiththeDataSocketServerManager.

ChangesthatyoumaketotheDataSocketServerusingtheDataSocketServerManagertakeeffectthenexttimeyoulaunchtheDataSocketServer.IfyouchangetheDataSocketServerconfigurationintheDataSocketServerManagerwhiletheDataSocketServerisrunning,youmustshutdownandlaunchtheDataSocketServeragainbeforethechangestakeeffect.

YoucanperformthefollowingtaskswiththeDataSocketServerManager:LimitthetotalnumberofsimultaneousconnectionstotheDataSocketServerfromDataSocketReadersandDataSocketWritersLimitthenumberofdataitemsthatDataSocketclientsareallowedtodynamicallycreateontheDataSocketServerSetbufferingconstraintsforpredefineditemsanddynamicallycreateditemsAdduserstopermissiongroupsCreatenewpermissiongroupsCreatepredefineddataitemsImportandexportDataSocketServerManagerconfigurations

ConfiguringBufferingLaunchtheDataSocketServerManagerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServerManagertoconfigurebufferingconstraints.Bufferingconstraintssetthemaximumsizeofthebufferintermsofpacketsandintermsofbytes.Theseconstraintspreventabufferfromgrowingunboundedandconsumingexcessivememory.Completethefollowingstepstoconfigureserver-sidebufferingforpredefineddataitemsortotoconfiguredefaultbufferingconstraintsfordynamicallycreateddataitems.

BufferingConstraintsforPredefinedDataItems1. Createapredefineddataitem.Bydefault,theDataSocketServer

Managersetsthemaximumbuffersizeto25MBand1packet,effectivelyprovidingunbufferedbehavior.

2. Tooverridethedefaultbufferingconstraints,selectthedataitemfromthePredefinedDataItemscategoryandspecifynewMaxBufferBytesandMaxBufferPacketsvalues.

BufferingConstraintsforDynamicallyCreatedDataItemsYoucanspecifydefaultbufferingconstraintsthatapplytoalldataitemscreateddynamicallyontheDataSocketServer.AnydynamicdataitemresidingontheDataSocketServerinheritsthedefaultbufferingconstraintswhentheDataSocketServercreatesthedataitem.

1. SelectDfltBufferMaxBytesfromtheServerSettingscategoryandsetthenewmaximumbuffersizeinbytes.

2. SelectDfltBufferMaxPacketsfromtheServerSettingscategoryandsetthenewmaximumbuffersizeinpackets.

ConfiguringPermissionstotheDataSocketServerYoucancategorizeusersaccordingtohowtheyinteractwiththeDataSocketServerandwhatpermissiontheyneedforconnectingtotheDataSocketServer.Differentpermissiongroupsincludereadaccess,writeaccess,dataitemcreators,andadministrators.Youalsocandefinenewpermissiongroups.Usethepermissiongroupstogrouphostswithsimilarneeds.TheDataSocketServerManagerprovidesthefollowingdefaultgroups:

TheAdministratorspermissiongroupisreservedforfutureuseandmainlyintendedforretrievingmanagementinformationfromtheDataSocketServer.TheDefaultReaderspermissiongroupcanreadalldynamicallycreateddataitemsfromtheDataSocketServer.Inaddition,theDefaultReaderspermissiongroupcanreadfromanypredefineddataitemthathasitsreadaccessgroupsettoDefaultReaders.TheDefaultWriterspermissiongroupcanwritetoalldynamicallycreateddataitemsontheDataSocketServer.Inaddition,theDefaultWriterspermissiongroupcanwritetoanypredefineddataitemthathasitswriteaccessgroupsettoDefaultWriters.TheCreatorspermissiongroupcandynamicallycreatenewdataitemsontheDataSocketServer.

Completethefollowingstepstoaddausertoadefaultgroup:1. LaunchtheDataSocketServerManagerbyselecting

Start»Programs»NationalInstruments»DataSocket»DataSocketServerManager.

2. SelectthegroupfromthePermissionGroupslist.3. ClicktheAddHostbuttontoaddausertothegroup.4. AddtheusertothepermissiongroupusingeitherthenameorIPaddress

indotteddecimalnotationofthecomputer.TheDataSocketServerManageralsohastwovariables,localhostandeveryhost;localhostrepresentsthelocalcomputer(thecomputerwheretheserverisrunning)andeveryhostrepresentsallcomputers(unrestrictedaccess).

CreatingPermissionGroupsYoucancreatenewpermissiongroupsforothersetsofusers.Forexample,youmightneedapermissiongroupthatreadsonlypredefineddataitems,unliketheDefaultReadersgroup.Predefineditemscanhavespecialreadandwriteaccessgroups.Youcanspecifywhichgroupscancreateitems,writeitems,andreaditems.Asaresult,differentcomputerscanhaveindividualizedaccesstodifferentpredefineditems.Completethefollowingstepstocreateanewpermissiongroupthatreadsorwritestoapredefineddataitem.

1. LaunchtheDataSocketServerManagerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServerManager.

2. ClicktheNewGroupbutton.3. EnteradescriptivenameforthepermissiongroupintheNametextbox.4. ModifytheHostslisttoincludethecomputerstowhichyouwantto

grantaccess.YoucanspecifyacomputereitherbythecomputernameonthenetworkortheIPaddressindotteddecimalnotation.TheDataSocketServerManageralsohastwovariables,localhostandeveryhost;localhostrepresentsthelocalcomputer(thecomputerwheretheserverisrunning)andeveryhostrepresentsallcomputers(unrestrictedaccess).

5. SelectthedataitemtowhichyouwanttograntaccessfromthePredefinedDataItemslist,andthenselectthenewpermissiongroupfromtheReadAccessorWriteAccesspull-downmenu.

CreatingPredefinedDataItemsontheDataSocketServerYoucanspecifydataitemsthatmustbeautomaticallycreatedandinitializedwhenyoulaunchtheDataSocketServer.AsyoucreateDataSocketclients,considerdefiningthedataitemsintheDataSocketServerManagersothatyoucandefineaccesspermissiongroupsforthedataitems.CompletethefollowingstepstopredefineadataitemonaDataSocketServer.

1. LaunchtheDataSocketServerManagerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServerManager.ThePredefinedItemscategorylistsallitemsthattheDataSocketServercreateseachtimeyoulaunchit.TheseitemsexistwithoutDataSocketclientconnections,unlikedynamicallycreateditemsthatexistonlyduringaDataSocketclientconnection.

2. ClicktheNewItembutton.3. EnteradetaileddescriptionfortheitemintheDescriptiontextbox.For

example,youmightlistthedatasource,thedatatype,andaccesspermissions.

4. EnteradescriptivenameforthedataitemintheNametextbox.5. Grantreadandwriteaccesstopermissiongroupsbyselectingthe

appropriatepermissiongroupfromtheReadAccessandWriteAccesspull-downmenus.

6. IfyouwanttoallowmultiplewriterstoconnecttotheDataSocketServer,placeacheckmarkintheAllowMultipleWriterscheckbox.

7. SpecifythedatatypeandavaluefortheInitialValue.RememberthatpredefineddataitemsexistevenwithoutaDataSocketclientconnection.IfaDataSocketReaderisconnectedtoapredefineddataitemontheDataSocketServerbeforeaDataSocketWriterisconnected,theDataSocketServerreturnstheinitialvaluetotheReader.DataSocketWritersoverwritedefaultvalues;whenaDataSocketWriterwritestoapredefineddataitem,thatitemretainsthevalueeveniftheDataSocketWriterdisconnectsfromtheserver.AfteraDataSocketWriteroverwritestheinitialvalueofapredefineditem,theitemdoesnotreturntotheinitialvalueunlesstheDataSocketServerisshutdownandrelaunched.

LimitingtheNumberofDynamicallyCreatedDataItemsCompletethefollowingstepstolimitthenumberofdataitemstheDataSocketServercandynamicallycreate.

1. LaunchtheDataSocketServerManagerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServerManager.

2. SelectMaxItemfromtheServerSettingscategory.3. Setthemaximumnumberofdataitemsyouwanttoallowthe

DataSocketServerrunningonthelocalcomputertodynamicallycreate.TheDataSocketServercancreatebetween1and1000dynamicdataitems,whichdoesnotincludepredefineddataitems.Thedefaultis200.

SavingDataSocketServerConfigurationsYoucancreatemultipleDataSocketServerconfigurationsandimportandexportthem,whichisespeciallyusefulwhenyouwantaDataSocketServeronanothercomputertohavethesameconfigurationastheoneonthelocalcomputerbecauseyoucannotconfiguretheDataSocketServerremotelyorprogrammatically.YoumustlocallyconfiguretheDataSocketServerwiththeDataSocketServerManager.Bydefault,theDataSocketServerusestheconfigurationspecifiedincwdssini.dss,whichexistsinthesamedirectoryastheDataSocketServerexecutable.

SavingDefaultConfigurationsAfteryouconfiguresettingsintheDataSocketServerManager,selectSettings»SaveSettingsNowtosavethesettingstocwdssini.dss.

ImportingConfigurationsToimportsettingsfromanotherfile,selectSettings»ImportSettingsandselectafilefromtheOpenDataSocketServerconfigurationdialogbox.

ExportingConfigurationsTosavethecurrentconfigurationoftheDataSocketServersoyoucanloaditonanothercomputeroratalatertime,selectSettings»ExportSettingsandselectafilefromtheSaveDataSocketServerconfigurationdialogbox.

SettingConnectionLimitsCompletethefollowingstepstolimitthenumberofsimultaneousconnectionstotheDataSocketServer.

1. LaunchtheDataSocketServerManagerbyselectingStart»Programs»NationalInstruments»DataSocket»DataSocketServerManager.

2. SelectMaxConnectionsfromtheServerSettingscategory.3. Setthemaximumnumberofsimultaneousconnectionsyouwantto

allowtotheDataSocketServerrunningonthelocalcomputer.YoucansetMaxConnectionsbetween1and1000.Thedefaultis50.

BufferingBufferingisaDataSocketTransferProtocol(DSTP)featurethatminimizesthelikelihoodthataDataSocketServerwilldropdatavalues.Withbuffering,theDataSocketServertemporarilystoresthevaluespublishedtoadataiteminafirst-in,first-out(FIFO)bufferforthedataitembeforesendingthedatatosubscribingclients.Providedthatabufferneverexceedsitscapacity,bufferingpreventsunprocessedvaluesfrombeingoverwrittenanddroppedbytheDataSocketServer.YoucanconfigureindividualbufferingconstraintsforeachpredefineddataitemonaDataSocketServeroryoucanconfiguredefaultbufferingconstraintsforalldynamicallycreateddataitems.

NoteSomeapplicationdevelopmentenvironmentssuchasLabVIEWmaintainclient-sidebuffersinadditiontotheserver-sidebuffer.Tominimizedataloss,setthebufferingconstraintsforboththeDataSocketServerandthesubscribingDataSocketclients.RefertotheLabVIEWHelpforinformationaboutclient-sidebufferinginLabVIEW.

SometimestheDataSocketServerwillhavetodropvaluestoenforcethebufferingconstraintsforadataitem.WhentheDataSocketServerneedstodropavalue,itdropsvaluesfromthefrontofabuffer—thatis,itdropsolderdatainfavorofnewerdata.Morespecifically,theDataSocketServerdropsavaluefromthefrontofabufferwhenoneofthefollowingconditionsistrue:

Allclientscurrentlysubscribedtothedataitemhavereceivedthevalue,orInsertinganewvalueintothebackofthebufferviolateseitherofthetwobufferingconstraintsthatyousetforthatdataitem.

TheDataSocketServerdoesnotnotifyDataSocketReadersorWriterswhenitdropsdatavalues.DataSocketWriterscanaddasequencenumberattributetothepublisheddata,soDataSocketReaderscandetectdroppedvaluesinadatastreambycheckingthesequencenumberattribute.

DataSocketServerDiagnosticsUtilityTolaunchtheDataSocketServerDiagnosticsutility,selectTools»DiagnosticsintheDataSocketServer.UsethisutilitytoviewinformationabouttheactivedataitemsontheDataSocketServerandtofine-tunebufferingconstraints.

ViewingInformationaboutDataItemsToviewinformationaboutaspecificdataitem,selectthedataitemfromthetreeintheleftpaneofthewindow.Intherightpaneofthewindow,youcanfindinformationabouttheDataSocketclientscurrentlysubscribingtothedataitem,bufferingconstraints,bufferutilization,andnumberofpacketsthatweredropped.

AdjustingBufferingConstraintsYoucanadjustthebufferingconstraintsintheDataSocketServerDiagnosticsutilitytofine-tuneperformance.Toupdateabufferingconstraintforadataitem,selectthedataitem,updatetheBytesorPacketsconstraintvalueinthenumericcontrol,andclicktheUpdatebuttontoapplythenewconstraint.Afteryoufine-tunethebufferingconstraints,savethesettingstotheDataSocketServerconfigurationfilebyselectingFile»SaveSettings.

NoteWhenyousavedataitemsandnewbufferingconstraintstotheconfigurationfile,yousaveonlypredefineddataitems,notdynamicallycreateddataitemscurrentlypublishedontheDataSocketServer.TheDataSocketServersavespredefineddataitemswiththeirinitialvalues,nottheircurrentvalues.

ReadingfromaDataSocketServerUseNILabVIEW,LabWindows/CVI,orMeasurementStudiotocreateaDataSocketReaderapplication.ADataSocketReaderapplicationsubscribestolivedatabeingpublishedbyaDataSocketWriterapplicationtoaDataSocketServer.UsetheDataSocketAPIsprovidedinLabVIEW,LabWindows/CVI,andMeasurementStudiotocreateaVIorapplicationthatconnectstotheDataSocketServerusingaURLandretrievesliveupdatesasnewdataispublishedtotheDataSocketServer.

NoteYoumusthaveInternetExplorer3.0orlaterinstalledonWindowscomputersonwhichyourunDataSocketReadersorWriters.

RefertotheLabVIEWHelp,LabWindows/CVIHelp,orMeasurementStudioHelpforinformationaboutcreatingaDataSocketReaderVIorapplication.

WritingtoaDataSocketServerUseNILabVIEW,LabWindows/CVI,orMeasurementStudiotocreateaDataSocketWriterapplication.ADataSocketWriterapplicationpublisheslivedatatoaDataSocketServer.UsetheDataSocketAPIsprovidedinLabVIEW,LabWindows/CVI,andMeasurementStudiotocreateaVIorapplicationthatconnectstotheDataSocketServerusingaURLandpublishesupdatesthataDataSocketReaderapplicationcanretrieve.

NoteYoumusthaveInternetExplorer3.0orlaterinstalledonWindowscomputersonwhichyourunDataSocketReadersorWriters.

RefertotheLabVIEWHelp,LabWindows/CVIHelp,orMeasurementStudioHelpforinformationaboutcreatingaDataSocketWriterVIorapplication.

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RelatedDocumentationThefollowingdocumentscontaininformationthatyoumightfindhelpfulasyouusethishelpfile:

LabVIEWHelpMeasurementStudioHelpLabWindows/CVIHelp

ImportantInformationWarrantyCopyrightTrademarksPatentsWarningRegardingUseofNIProducts

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