<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.serviceModel>
      <client>
        <endpoint address="http://127.0.0.1:9999/calculatorservice" binding="wsHttpBinding"  contract="Contracts.ICalculator" name="calculatorservice" />
      </client>
    </system.serviceModel>
</configuration>WCF中的“endpoint”到底什么作用?怎样理解?