Hie,
For the first time, I have enabled the SRU on Zebra server by editing koha-conf.xml :
<listen id="publicserver" >tcp:@:9999</listen>
<server id="publicserver" listenref="publicserver">
<directory>/var/lib/zebradb/biblios</directory>
<config>/etc/koha/zebradb/zebra-biblios.cfg</config>
<cql2rpn>/etc/koha/zebradb/pqf.properties</cql2rpn>
<retrievalinfo>
<retrieval syntax="usmarc" name="F" />
<retrieval syntax="usmarc" name="B" />
</retrievalinfo>
</server>
<serverinfo id="publicserver">
<ccl2rpn>/etc/koha/zebradb/ccl.properties</ccl2rpn>
<user>xxxx</user>
<password>xxxx</password>
</serverinfo>