c# - WCF web service is too busy -

i have problem busy wcf service through clients can connect , consume it. below error , stack trace on server configuration , attributes of class.

error message , stacktrace:

the http service located @ https://my.web.service.com/service/service.svc unavailable.  because service busy or because no endpoint found listening @ specified address. please ensure address correct , try accessing service again later.exst:  server stack trace:     @ system.servicemodel.channels.httpchannelutilities.processgetresponsewebexception(webexception webexception, httpwebrequest request, httpabortreason abortreason)    @ system.servicemodel.channels.httpchannelfactory`1.httprequestchannel.httpchannelrequest.waitforreply(timespan timeout)    @ system.servicemodel.channels.requestchannel.request(message message, timespan timeout)    @ system.servicemodel.channels.securitychannelfactory`1.securityrequestchannel.request(message message, timespan timeout)    @ system.servicemodel.security.securitysessionsecuritytokenprovider.dooperation(securitysessionoperation operation, endpointaddress target, uri via, securitytoken currenttoken, timespan timeout)    @ system.servicemodel.security.securitysessionsecuritytokenprovider.gettokencore(timespan timeout)    @ system.identitymodel.selectors.securitytokenprovider.gettoken(timespan timeout)    @ system.servicemodel.security.securitysessionclientsettings`1.clientsecuritysessionchannel.onopen(timespan timeout)    @ system.servicemodel.channels.communicationobject.open(timespan timeout)    @ system.servicemodel.channels.servicechannel.onopen(timespan timeout)    @ system.servicemodel.channels.communicationobject.open(timespan timeout)    @ system.servicemodel.channels.servicechannel.callopenonce.system.servicemodel.channels.servicechannel.icallonce.call(servicechannel channel, timespan timeout)    @ system.servicemodel.channels.servicechannel.calloncemanager.callonce(timespan timeout, calloncemanager cascade)    @ system.servicemodel.channels.servicechannel.call(string action, boolean oneway, proxyoperationruntime operation, object[] ins, object[] outs, timespan timeout)    @ system.servicemodel.channels.servicechannelproxy.invokeservice(imethodcallmessage methodcall, proxyoperationruntime operation)    @ system.servicemodel.channels.servicechannelproxy.invoke(imessage message) 

web server configuration:

<?xml version="1.0"?> <configuration>   <configsections>     <sectiongroup name="applicationsettings" type="system.configuration.applicationsettingsgroup, system, version=4.0.0.0, culture=neutral, publickeytoken=b77a5c561934e089">       <section name="server.properties.settings" type="system.configuration.clientsettingssection, system, version=4.0.0.0, culture=neutral, publickeytoken=b77a5c561934e089" requirepermission="false"/>       <section name="serveredi.properties.settings" type="system.configuration.clientsettingssection, system, version=4.0.0.0, culture=neutral, publickeytoken=b77a5c561934e089" requirepermission="false"/>     </sectiongroup>   </configsections>    <system.web>     <httpruntime maxrequestlength="65536"/>     <customerrors mode="off"/>     <compilation targetframework="4.5"/>     <pages controlrenderingcompatibilityversion="4.0"/>   </system.web>    <system.servicemodel>      <bindings>       <wshttpbinding>         <binding name="iwebservice" closetimeout="01:00:00" opentimeout="01:00:00" receivetimeout="01:00:00" sendtimeout="01:00:00" allowcookies="false" bypassproxyonlocal="false" hostnamecomparisonmode="strongwildcard" maxbufferpoolsize="2147483647" maxreceivedmessagesize="2147483647" messageencoding="text" textencoding="utf-8" usedefaultwebproxy="true">           <readerquotas maxdepth="2147483647" maxstringcontentlength="2147483647" maxarraylength="2147483647" maxbytesperread="2147483647" maxnametablecharcount="2147483647"/>           <security mode="transportwithmessagecredential">             <transport clientcredentialtype="none" proxycredentialtype="none" realm=""/>             <message clientcredentialtype="username" negotiateservicecredential="true"/>           </security>         </binding>       </wshttpbinding>     </bindings>      <services>       <service behaviorconfiguration="nowa" name="serviceweb.webservice">         <endpoint address="" binding="wshttpbinding" bindingconfiguration="iwebservice"           contract="serviceweb.iwebservice" />       </service>     </services>      <behaviors>       <servicebehaviors>         <behavior name="nowa">           <servicemetadata httpsgetenabled="true"/>           <servicecredentials>             <servicecertificate findvalue="xxxyyyzzz.com" storelocation="localmachine" x509findtype="findbysubjectname"/>             <usernameauthentication usernamepasswordvalidationmode="custom" customusernamepasswordvalidatortype="serviceweb.mycustomusernamepasswordvalidator,serviceweb"/>             <windowsauthentication includewindowsgroups="false" allowanonymouslogons="false"/>           </servicecredentials>           <serviceauthorization impersonatecallerforalloperations="false"/>           <datacontractserializer maxitemsinobjectgraph="2147483647"/>           <servicedebug includeexceptiondetailinfaults="true"/>           <servicethrottling maxconcurrentcalls="500" maxconcurrentinstances="500" maxconcurrentsessions="500" />          </behavior>        </servicebehaviors>     </behaviors>     <servicehostingenvironment multiplesitebindingsenabled="true"/>   </system.servicemodel>    <startup>     <supportedruntime version="v4.0" sku=".netframework,version=v4.0"/>   </startup>    <system.webserver>     <urlcompression dostaticcompression="false"/>   </system.webserver>  </configuration>    

class attributes:

[servicebehavior(instancecontextmode = instancecontextmode.single)]    //[servicebehavior(instancecontextmode = instancecontextmode.percall, concurrencymode = concurrencymode.single)]   //  [servicebehavior(instancecontextmode = instancecontextmode.percall,    //              concurrencymode = concurrencymode.multiple)]     public class webservice : iwebservice {} 

if grateful cases described on stackoverflow not fit , solve case. @ moment service using 50 customers. problem comes when call method returns , can not call asynchronously, because answer must delivered.

wcf has default throttling values, hitting these, see: http://blogs.msdn.com/b/wenlong/archive/2009/07/26/wcf-4-higher-default-throttling-settings-for-wcf-services.aspx

normally error when client not close connection, connections open until timeout, blocking new calls.