title: how to stop False alert in zabbix while monitoring any port or service in zabbix
body: <p>My zabbix server sends alerts immediately when a service gets failed </p>
  
  <p>my item for monitoring a port:</p>
  
  <pre><code>net.tcp.listen[80]
  </code></pre>
  
  <p>my trigger for monitoring a port:</p>
  
  <pre><code>{Testserver:net.tcp.listen[80].last()}=0
  </code></pre>