This file is required for the sample to run. There was a 512-bit version in master:
https://github.com/cpp-netlib/cpp-netlib/blob/master/libs/network/example/http/ssl/dh512.pem
which this replaces.

Since Heartbleed and POODLE, Google Chrome no longer accepts 512-bit DH keys.

An end user should obviously replace these files for production usage. But for the purpose of the example, I don't see a security risk.

I built that version:
openssl dhparam -outform PEM -out dh2048.pem 2048

Ideally they would be autogenerated by the build. I can see if I can learn enough cmake magic to make that happen? I don't know enough about the build-bot to know if that would work, but I can try.

Thanks for the explanation -- yes, we can fix this later. I'll merge this now.

Cheers