You can force this message executing: $ echo | nc SERVER_IP 5432 2014-11-04 21:44:37 CET LOG: incomplete startup packet
What do you need help on? PG uses a binary protocol, you sent it bad data ( I think this will open connection, send a \n byte, shutdown it ) and it complained in the first check ( I suppose it is due to the connection expecting an startup packet with a given format, and it couldn't get it because it's longer than 1 byte, everything is prety well documented, RTFM ).
