[Solved]Can any body help me debug this app?(use lettre crate)

By the way, is there any openbox tools to debug rust app?

There shouldn’t be any appreciable difference between starting the application directly and via cargo run. I notice that your successful run uses an IPv4 address, while the hanging one uses IPv6. Try to find out if there are lower-level networking issues at play.

(I tried your code with a dual-stack server, but reachable from the client only via IPv4. It worked with cargo run. The client is a CentOS 7 machine.)

Thank you.
I have update my github issue(it uses ipv4 now).I feel there may be something wrong with openssl in my machine,I will test it next day.

I have three different versions of openssl in my system, the problem disappeared after remove them.