Allow defmt-print to connect to a TCP port.

[hydra]

Why: The Segger J-Link debugger sessions listen on TCP port 19021 by default and it dumps RTT output to any client that connects to the port.

This allows defmt-print to log data so you can see it in real-time while you are debugging in your IDE.

example:

$ defmt-print tcp --host=127.0.0.1 --port=19021

Output from --help is now:

Prints defmt-encoded logs to stdout

Usage: defmt-print.exe [OPTIONS] -e <ELF> [COMMAND]

Commands:
  stdin
  tcp
  help   Print this message or the help of the given subcommand(s)

Options:
  -e <ELF>
      --json
      --show-skipped-frames
  -v, --verbose
  -V, --version
  -h, --help                 Print help

Default subcommand is std-in for backwards compatibility.

The host and port can read from your environment variables RTT_HOST and RTT_PORT respectively.

$ defmt-print tcp --help
Usage: defmt-print.exe -e <ELF> tcp --host <HOST> --port <PORT>

Options:
  -h, --host <HOST>  [env: RTT_HOST=]
  -p, --port <PORT>  [env: RTT_PORT=]
  -h, --help         Print help

C:\> set RTT_HOST=127.0.0.1
C:\> set RTT_PORT=19021

or

$ export RTT_HOST=127.0.0.1
$ export RTT_PORT=19021

Once environment variables are set they are shown and used appropriately.

$ defmt-print tcp --help
Usage: defmt-print.exe -e <ELF> tcp --host <HOST> --port <PORT>

Options:
  -h, --host <HOST>  [env: RTT_HOST=127.0.0.1]
  -p, --port <PORT>  [env: RTT_PORT=19021]
  -h, --help         Print help
$ defmt-print -e <elf> tcp
...

J-Link console:

CLion debug session of the target:

defmt-print output:

This is a replacement PR for #676
EDIT: I updated the examples to show the 0.3.7 output, the original comment previously had the 0.3.2 output

[hydra]

This also works with OpenOCD

example GDB commands:

monitor rtt setup 0x24008000 8192 "SEGGER RTT"
monitor rtt polling_interval 5
monitor rtt start
monitor rtt server start 8765 0

defmt-print -e <elf> tcp --host localhost --port 8765

[hydra]

Changelog updated and cargo fmt suggestions applied.

[Urhengulas]

@hydra I added a few changes. Let me know what you think.

And can you please test it as well? I don't have the J-Link debugger set up.

[hydra]

@Urhengulas will test hopefully later today and get back to you.

[hydra]

Ok @Urhengulas so I did a review of your comments and everything 'looks' ok, but didn't work with my saved 'external tools' configuration in IntelliJ that I've been using since I did the original PR.

The issue is with commit 8b60a4c -> "Switch from String to IpAddr"

Where things go wrong is like this:

$ defmt-print.exe -e target/thumbv7em-none-eabihf/release/nucleoh743zi2 tcp --host localhost --port 8765
error: invalid value 'localhost' for '--host <HOST>': invalid IP address syntax

I have been supplying hostnames, not just IP address, on the command line. Usually you want it to work for both, especially for the use-case of an internet-connected J-Link or OpenOCD connected debugger that uses a DDNS hostname. You can also see this in one of my comments on this PR, here: #757 (comment)

Additional, commit a5348ec -> "Add default values" should probably be using 'localhost' instead of an IP address.

The actual functionality of reading frames over TCP works for me still when an IP address is used, e.g.

$ defmt-print.exe -e target/thumbv7em-none-eabihf/release/nucleoh743zi2 tcp --host 127.0.0.1 --port 8765
0 INFO  Reset
└─ startup::isr::reset_handler @ logging\src\tracing.rs:82

Not sure what to suggest at this point. Options:

1. Merge original PR as-is. Add another PR for cleanups that still allow hostnames to be used later.
2. Update this PR with additional commits that allow hostnames to be used again.
3. Merge this PR as-is. Add another PR that allow hostnames to be used again.

I'm keen to get the basic functionality of reading defmt frames over TCP to be merged in, so perhaps 1 or 3 might be better depending on your availability/schedule?

[Urhengulas]

Hostnames should work now. Can you please test again. If it does work we can merge it.

[hydra]

Hostnames should work now. Can you please test again. If it does work we can merge it.

Hi, I just grabbed the PR change, simpler than I thought it was going to be, nice!

It seems to work fine, no error message when using hostname on the command line now.

$ defmt-print.exe -e target/thumbv7em-none-eabihf/debug/config tcp --host localhost --port 8765
0 TRACE Config
└─ config::main @ src\bin\config.rs:39

LGTM!