Serial console tcp server+multiplexer and web client

TCP Server

This small program is meant for sharing a serial port into network so that it can be accessed with telnet, for example.

The console server allows basically unlimited number of concurrent client connections. All clients will see the same serial port data, since it is replicated to all clients.

Write support has to be separately enabled with -w option. Otherwise, all tcp connections are read only, i.e. nothing can be written into the serial port. If write is enabled, any client can write to the console. The included web client does not support writing. Something like telnet or nc have to be used for that.

A note about security: there is none. No ACL, no encryption, no authentication. Nothing. You should probably use this only over ssh connections with tcp port forwarding and limit the console server listening only on localhost.

This program was initially written just for learning Rust. It is kind of slightly improved re-implementation of my old code written in Python.

``` USAGE: console-server [FLAGS] [OPTIONS]

FLAGS: -d, --debug -h, --help Prints help information -t, --trace -V, --version Prints version information -w, --write

OPTIONS: -l, --listen [default: 127.0.0.1:24242] -b, --ser-baud [default: 9600] --ser-datab [default: 8] --ser-flow [default: none] --ser-parity [default: N] --ser-stopb [default: 1] -s, --serial-port [default: /dev/ttyUSB0]

```

Web client

``` USAGE: console-client [FLAGS] [OPTIONS]

FLAGS: -d, --debug -h, --help Prints help information -t, --trace -V, --version Prints version information

OPTIONS: -c, --connect [default: 127.0.0.1:24242] -l, --listen [default: 127.0.0.1:8080] --template-dir [default: templates] ```

The console client starts a small internal web server with hyper at the designated listen address. The index page from index() is simple, and includes HTML code to create a line-oriented console window. The HTML is rendered from a Sailfish template.

HTML console window is utilizing an event-stream that is provided by the same web-server from client().

Rudimentary URL/request routing is handled with the function req_router().

The event-stream output is line-oriented and using a DIY input Decoder that was basically stolen from tokio_util LinesCodec and modified heavily to wrap long lines and replace non-printable characters with underscores. It is a bit brutal but works.

Sample run:

$ ./target/debug/console-client [2021-07-30T10:09:41Z INFO console_client] Starting up console-client... [2021-07-30T10:09:41Z INFO console_client] Template directory: templates [2021-07-30T10:09:42Z INFO console_client] Found templates: [console.html.tera] [2021-07-30T10:09:44Z INFO console_client] 127.0.0.1:40968 GET /client/

testing with wget:

``` $ wget -qS -O- http://localhost:8080/client/ HTTP/1.1 200 OK content-type: text/event-stream; charset=utf-8 cache-control: no-cache transfer-encoding: chunked date: Fri, 30 Jul 2021 10:09:44 GMT retry: 999999 id: 1 data: * Connected to: /dev/ttyUSB0

```

Please note that there was also a console-server running at port 24242 to provide the actual serial port access.