Support sending messages to Erlang/LFE servers

[oubiwann]

This is in support of the MIDI clock tracking that undermidi needs to do in support of VCV Rack interop.

Tasks:

• Add basic TCP client
• Add function for connecting to epmd
• Add function for getting node port from epmd
• Add CLI command for getting node port from epmd
• Add function for connecting to remote host
• Create functions for generating Erlang RPC/ERPC payloads
• Create functions for making RPC calls to Erlang/LFE servers
• Add configuration option for an RPC server
• Update the MIDI receive callbacks to hit configured RPC servers

Blocks:

• Create new gen_servers in support of external MIDI clocks ut-proj/undermidi#41

Related:

• Add support for receiving MIDI from devices #22
• Feature/22/midi receive #25
• Add VCV modular synth support ut-proj/undermidi#38

[oubiwann]

Maybe this for basic TCP client?

• https://gist.github.com/adeekshith/34c20eb45bebe41f5247

[oubiwann]

Documentation on dist protocol:

• https://www.erlang.org/doc/apps/erts/erl_dist_protocol.html

Notes for use:

• https://elixirforum.com/t/implementing-the-distribution-protocol-in-other-languages/20610/9
• https://www.erlang-solutions.com/blog/erlang-and-elixir-distribution-without-epmd/

[oubiwann]

Ah, perfect:

• https://github.com/ergo-services/ergo/blob/master/node/epmd.go#L249

[oubiwann]

Parsing the result:

• https://github.com/ergo-services/ergo/blob/master/node/epmd.go#L206

And maybe this:

• https://pkg.go.dev/github.com/go-restruct/restruct

[oubiwann]

Hrm, until full OTP node support has landed (see #27) I don't think we're going to be able to get responses after sending an RPC message ... just going to have to fire into the void.

[oubiwann]

The MIDI callback func has been updated to take the RPC client as a parameter. Once the external clock state machine is done, this client will be used to update the state machine when the MIDI clock message fires off the callback.