How to make Jetty webserver listen on port 80?

You will need to edit the /etc/jetty/jetty.xml file. Look for a paragraph that says:

<Call name="addConnector">
      <Arg>
          <New class="org.mortbay.jetty.nio.SelectChannelConnector">
            <Set name="host"><SystemProperty name="jetty.host" /></Set>
            <Set name="port"><SystemProperty name="jetty.port" default="8090"/></Set>
            <Set name="maxIdleTime">30000</Set>
            <Set name="Acceptors">2</Set>
            <Set name="statsOn">false</Set>
            <Set name="confidentialPort">8443</Set>
        <Set name="lowResourcesConnections">5000</Set>
        <Set name="lowResourcesMaxIdleTime">5000</Set>
          </New>
      </Arg>
    </Call>

Change the jetty.port Property to 80 as follows:

<Set name="port"><SystemProperty name="jetty.port" default="80"/></Set>

Restart jetty. That should do it.

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Since the above method did not work for OP, and running as root is discouraged, there is an alternative method, as mentioned in this document.