epee: only parse valid port

[selsta]

Reported by hacksandhops and Ada Logic.

[iamamyth]

Windows build fails on this branch. I didn't inspect the output close enough to tell if the failure owes to the new code, but I note a problem with boost string code, and this commit introduces a new boost string-related call.

[nahuhh]

Windows build fails on this branch. I didn't inspect the output close enough to tell if the failure owes to the new code, but I note a problem with boost string code, and this commit introduces a new boost string-related call.

I think the failure is unrelated, caused by boost version 1.89 issues. The windows CI has been failing for a while

cc @0xFFFC0000

[selsta]

yes, build failure is unrelated

[0xFFFC0000]

Windows build is something related to ICU and boost.locale. It started when pacman switched to boost 1.89. I am looking into this as we speak [1].

https://github.com/msys2/MINGW-packages/pull/25219/files