In those days, travellers were very shy of being confidential on a short notice, for anybody on the road might be a robber or in league with robbers.
I understand the meaning in general which describes the fact that people didn't trust each other, and were confidential about their privacy. But Dickens uses "shy of being confidential" that seems contradicted to me, because people wanted to be confidential, then why does he use "shy of being confidential"? Also, does "on a short notice" mean people greeting each other at the first time they meet?