about class Dcitionary

As you kownn, snort works on packet data, while Bro works on connection

Bro also has a signature engine that can read Snort rules, per the

want to know how to use Bro to save all the connection to dist file.

I don't quite know what you mean. Bro writes connection summaries to
stdout if you load tcp.bro (or the usual load of mt.bro). It also can
write a tcpdump packet trace file if you specify -w file.