open terminal in Ubuntu or Debian
koha-z3950-responder --enable <instancename> for example library
Start the server with:
koha-z3950-responder --start <instancename>
if any error occurred , download z3950_responder.pl from below
copy this file into /usr/share/koha/lib/misc/z3950_responder.pl
if the misc is not available in lib directory then create new directory and copy z3950_responder.pl in it.
then issue the command koha-z3950-responder --start <instancename>
your z39.50 responder will start.
The default port is 2100 (if you need to change, follow the given instruction)
Modify config.xml ie.g. to change the listening port from the default (2100). pqf.properties defines rules for translating the incoming Z39.50 queries, and may need to be customized for any custom search fields.