May be the problem with service configuration.
<system.servicemodel>
<services>
<service name="WcfService_using_callbacks_via_tcp.Service1">
behaviorConfiguration="Behavior_Service1">
<host>
<baseaddresses>
<add baseaddress="net.tcp://localhost:5050/Service1" />
</baseaddresses>
</host>
<endpoint address="" contract="WcfService_using_callbacks_via_tcp.IService1">
binding="netTcpBinding" bindingConfiguration="DuplexNetTcpBinding_IService1" />
<endpoint address="mex" contract="IMetadataExchange" binding="mexTcpBindng" />
</endpoint></service>
</services>
...
</system.servicemodel>
For more info :
SOF
I hope this will help to you.