FTP after build with plugin.xml

I would like to FTP the results of a build to a development server. When I add the following code to .sencha/app/plugin.xml:

Code:

    <target name="-after-app-build">
        <echo>FTPing to server</echo>
        <ftp server="server_name" 
                 remotedir="temp" 
             userid="userId" 
             password="dontAsk" 
             passive="true" 
             verbose="true"> 
            <fileset dir="./"> 
                <include name="index.html" /> 
            </fileset> 
        </ftp>            
    </target>

...I get the following error on build:

Code:

[INF] -after-app-build:
[INF]      [echo] FTPing to server
[ERR] Problem: failed to create task or type ftp
Cause: the class org.apache.tools.ant.taskdefs.optional.net.FTP was not found.
        This looks like one of Ant's optional components.
Action: Check that the appropriate optional JAR exists in
        -ANT_HOME/lib
        -the IDE Ant configuration dialogs


Do not panic, this is a common problem.
The commonest cause is a missing JAR.


This is not a bug; it is a configuration problem

Searching on ​org.apache.tools.ant.taskdefs.optional.net.FTP lead me to the commons-net-3.3 JAR, which I downloaded and put in my {cmd}/lib folder.

What am I missing?