Switching from 9.1 to 9.5 on Ubuntu 16.04

Sorry if this has been covered before. If so I'd appreciate a heads up.

Could someone please refer me to the appropriate documentation for 
disabling 9.1 and enabling 9.5 on Ubuntu 16.04?

I have a production database running on 9.1 and can dump and reload 
without problem. I have tried the following ...

1. Dump from 9.1

2. sudo service postgresql stop (which returned without error)

3. Adjust (9.1) postgresql.conf port entry from 5432 to 5431

4. Adjust (9.5) postgresql.conf port entry to 5432

5 sudo service postgresql start (which returned without error)

When trying to createdb I'm getting the following error ...

createdb: could not connect to database template1: could not connect to 
server: Connection refused (0x0000274D/10061)
         Is the server running on host "pq4" (203.34.166.57) and accepting
         TCP/IP connections on port 5432?

For the moment I have restored the conf files, restarted and we are back 
in production.

Any hints appreciated

Thanks

Mike