Incorrect key pulled for Electron using TCP

[towynlin]

Given I have an Electron using TCP
When I run particle keys save electron-key-filename
Then I expect to receive the RSA key for the TCP server
But instead I currently receive the EC key for the UDP server

[brycekahle]

Community member just ran into this bug: https://community.particle.io/t/tls-key-for-local-server-cant-be-converted-to-der-format/27258

[m-mcgowan]

The keys commands expects a --protocol tcp argument. So, not sure this is a bug other than missing documentation?

So the question is what to do when --protocol is not provided. Here's a few options:

• for devices with a single protocol, default to that (current behaviour on Core/Photon/P1)
• for devices with multiple protocol support:
  • raise an error if --protocol is not specified. This makes it clear there are multiple protocols and that the user needs to be clear which one they mean. (But this is inconvenient for the majority who never change from the default.)
  • a more friendly alternative - inspect the device to determine the current protocol in use and default to that. Only raise the error above if for some reason the protocol cannot be determined.