Testing automation - Legacy system

We are in the process of moving from legacy system to UNIX system. Since it is production enterprise system, this need to be done by stages. So always need to keep legacy system running. This keeps us in supporting / testing both systems. We recently integrated Legacy system through SOCKET programming to test using ant script. Here is snippet,

<target name="legacytest">
    <telnet server="${legacy.host}" port="${legacy.port}"
 timeout="${legacy.timeout}" initialCR="yes">
 <read></read>
 <write>$NET:TYPE 6</write>
 <read>U#</read>
 <write>$NET:SET XON</write>
 <read>U#</read>
 <write>${legacy.login}</write>
 <read>UNITS</read>
   </telnet>
</target>

This does not come with standard ant installs, so commons-net-xxx.jar needs to be downloaded from this link and include under ant/lib directory.