lan-mouse/README.md

# Lan Mouse
- _Now with a gtk frontend_

Lan Mouse is a mouse and keyboard sharing software similar to universal-control on Apple devices.
It allows for using multiple pcs with a single set of mouse and keyboard.

The primary target is Wayland on Linux but Windows and MacOS have partial support as well (see below for more details).

<picture>
    <source media="(prefers-color-scheme: dark)" srcset="https://github.com/feschber/lan-mouse/assets/40996949/016a06a9-76db-4951-9dcc-127d012c59df">
    <source media="(prefers-color-scheme: light)" srcset="https://github.com/feschber/lan-mouse/assets/40996949/d6318340-f811-4e16-9d6e-d1b79883c709">
    <img alt="Screenshot of Lan-Mouse" srcset="https://github.com/feschber/lan-mouse/assets/40996949/016a06a9-76db-4951-9dcc-127d012c59df">
</picture>


Goal of this project is to be an open-source replacement for proprietary tools like [Synergy](https://symless.com/synergy), [Share Mouse](https://www.sharemouse.com/de/).

Focus lies on performance and a clean, manageable implementation that can easily be expanded to support additional backends like e.g. Android, iOS, ... .

***blazingly fast™*** because it's written in rust.

For an alternative (with slightly different goals) you may check out [Input Leap](https://github.com/input-leap).

## OS Support

The following table shows support for input emulation (to emulate events received from other clients) and
input capture (to send events *to* other clients) on different operating systems:

| Backend                   | input emulation          | input capture                        |
|---------------------------|--------------------------|--------------------------------------|
| Wayland (wlroots)         | :heavy_check_mark:       | :heavy_check_mark:                   |
| Wayland (KDE)             | :heavy_check_mark:       | :heavy_check_mark:                   |
| Wayland (Gnome)           | :heavy_check_mark:       | WIP                                  |
| X11                       | (WIP)                    | WIP                                  |
| Windows                   | ( :heavy_check_mark: )   | WIP                                  |
| MacOS                     | ( :heavy_check_mark: )   | WIP                                  |

Keycode translation is not yet implemented so on MacOS only mouse emulation works as of right now.

## Build and Run
Build in release mode:
```sh
cargo build --release
```

Run directly:
```sh
cargo run --release
```

### Conditional Compilation

Currently only x11, wayland and windows are supported backends,
Depending on the toolchain used, support for other platforms is omitted
automatically (it does not make sense to build a Windows `.exe` with
support for x11 and wayland backends).

However one might still want to omit support for e.g. wayland or x11 on
a Linux system.

This is possible through
[cargo features](https://doc.rust-lang.org/cargo/reference/features.html)

E.g. if only wayland support is needed, the following command produces
an executable with just support for wayland:
```sh
cargo build --no-default-features --features wayland
```

## Usage
### Gtk Frontend
By default the gtk frontend will open when running `lan-mouse`.

To add a new connection, simply click the `Add` button on *both* devices,
enter the corresponding hostname and activate it.

If the mouse can not be moved onto a device, make sure you have port `4242` (or the one selected)
opened up in your firewall.

### Command Line Interface
The cli interface can be enabled using `--frontend cli` as commandline arguments.
Type `help` to list the available commands.

E.g.:
```sh
$ cargo run --release -- --frontend cli
(...)
> connect <host> left|right|top|bottom
(...)
> list
(...)
> activate 0
```

### Daemon
Lan Mouse can be launched in daemon mode to keep it running in the background.
To do so, add `--daemon` to the commandline args:

```sh
$ cargo run --release -- --daemon
```

## Configuration
To automatically load clients on startup, the file `$XDG_CONFIG_HOME/lan-mouse/config.toml` is parsed.
`$XDG_CONFIG_HOME` defaults to `~/.config/`.

To create this file you can copy the following example config:

### Example config

```toml
# example configuration

# optional port (defaults to 4242)
port = 4242
# # optional frontend -> defaults to gtk if available
# # possible values are "cli" and "gtk" 
# frontend = "gtk"

# define a client on the right side with host name "iridium"
[right]
# hostname
host_name = "iridium"
# optional list of (known) ip addresses
ips = ["192.168.178.156"]

# define a client on the left side with IP address 192.168.178.189
[left]
# The hostname is optional: When no hostname is specified,
# at least one ip address needs to be specified.
host_name = "thorium"
# ips for ethernet and wifi
ips = ["192.168.178.189", "192.168.178.172"]
# optional port
port = 4242
```

Where `left` can be either `left`, `right`, `top` or `bottom`.

## Roadmap
- [x] Capture the actual mouse events on the server side via a wayland client and send them to the client
- [x] Mouse grabbing
- [x] Window with absolute position -> wlr\_layer\_shell
- [x] DNS resolving
- [x] Keyboard support
- [x] Scrollwheel support
- [x] Button support
- [ ] Latency measurement + logging
- [ ] Bandwidth usage approximation + logging
- [x] Multiple IP addresses -> check which one is reachable
- [x] Merge server and client -> Both client and server can send and receive events depending on what mouse is used where
- [x] Liveness tracking (automatically ungrab mouse when client unreachable)
- [ ] Clipboard support
- [x] Graphical frontend (gtk?)
- [ ] *Encryption*
- [x] respect xdg-config-home for config file location.

## Protocol
Currently *all* mouse and keyboard events are sent via **UDP** for performance reasons.
Each event is sent as one single datagram, currently without any acknowledgement to guarantee 0% packet loss.
This means, any packet that is lost results in a discarded mouse / key event, which is ignored for now.

**UDP** also has the additional benefit that no reconnection logic is required.
Any client can just go offline and it will simply start working again as soon as it comes back online.

Additionally a tcp server is hosted for data that needs to be sent reliably (e.g. the keymap from the server or clipboard contents in the future) can be requested via a tcp connection.

## Bandwidth considerations
The most bandwidth is taken up by mouse events. A typical office mouse has a polling rate of 125Hz
while gaming mice typically have a much higher polling rate of 1000Hz.
A mouse Event consists of 21 Bytes:
- 1 Byte for the event type enum,
- 4 Bytes (u32) for the timestamp,
- 8 Bytes (f64) for dx,
- 8 Bytes (f64) for dy.

Additionally the IP header with 20 Bytes and the udp header with 8 Bytes take up another 28 Byte.
So in total there is 49 * 1000 Bytes/s for a 1000Hz gaming mouse.
This makes for a bandwidth requirement of 392 kbit/s in total _even_ for a high end gaming mouse.
So bandwidth is a non-issue.

Larger data chunks, like the keymap are offered by the server via tcp listening on the same port.
This way we dont need to implement any congestion control and leave this up to tcp.
In the future this can be used for e.g. clipboard contents as well.

## Packets per Second
While on LAN the performance is great,
some WIFI cards seem to struggle with the amount of packets per second,
particularly on high-end gaming mice with 1000Hz+ polling rates.

The plan is to implement a way of accumulating packets and sending them as
one single key event to reduce the packet rate (basically reducing the polling
rate artificially).

The way movement data is currently sent is also quite wasteful since even a 16bit integer
is likely enough to represent even the fastest possible mouse movement.
A different encoding that is more efficient for smaller values like
[Protocol Buffers](https://protobuf.dev/programming-guides/encoding/)
would be a better choice for the future and could also help for WIFI connections.

## Security
Sending key and mouse event data over the local network might not be the biggest security concern but in any public network or business environment it's *QUITE* a problem to basically broadcast your keystrokes.
- There should be an encryption layer below the application to enable a secure link.
- The encryption keys could be generated by the graphical frontend.


## Wayland support
### Input Emulation (for receiving events)
On wayland input-emulation is in an early/unstable state as of writing this.

For this reason a suitable backend is chosen based on the active desktop environment / compositor.

Different compositors have different ways of enabling input emulation:

#### Wlroots
Most wlroots-based compositors like Hyprland and Sway support the following
unstable wayland protocols for keyboard and mouse emulation:
- [virtual-keyboard-unstable-v1](https://wayland.app/protocols/virtual-keyboard-unstable-v1)
- [wlr-virtual-pointer-unstable-v1](https://wayland.app/protocols/wlr-virtual-pointer-unstable-v1)

#### KDE
KDE also has a protocol for input emulation ([kde-fake-input](https://wayland.app/protocols/kde-fake-input)),
it is however not exposed to third party applications.

The recommended way to emulate input on KDE is the
[freedesktop remote-desktop-portal](https://flatpak.github.io/xdg-desktop-portal/#gdbus-org.freedesktop.portal.RemoteDesktop).

#### Gnome (TODO)
Gnome uses [libei](https://gitlab.freedesktop.org/libinput/libei) for input emulation,
which has the goal to become the general approach for emulating Input on wayland.


### Input capture

To capture mouse and keyboard input, a few things are necessary:
- Displaying an immovable surface at screen edges
- Locking the mouse in place
- (optionally but highly recommended) reading unaccelerated mouse input

|  Required Protocols  (Event Emitting)  | Sway               | Kwin                 | Gnome                |
|----------------------------------------|--------------------|----------------------|----------------------|
| pointer-constraints-unstable-v1        | :heavy_check_mark: | :heavy_check_mark:   | :heavy_check_mark:   |
| relative-pointer-unstable-v1           | :heavy_check_mark: | :heavy_check_mark:   | :heavy_check_mark:   |
| keyboard-shortcuts-inhibit-unstable-v1 | :heavy_check_mark: | :heavy_check_mark:   | :heavy_check_mark:   |
| wlr-layer-shell-unstable-v1            | :heavy_check_mark: | :heavy_check_mark:   | :x:                  |

The [zwlr\_virtual\_pointer\_manager\_v1](wlr-virtual-pointer-unstable-v1) is required
to display surfaces on screen edges and used to display the immovable window on
both wlroots based compositors and KDE.

Gnome unfortunately does not support this protocol
and [likely won't ever support it](https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/1141).

~In order for layershell surfaces to be able to lock the pointer using the pointer\_constraints protocol [this patch](https://github.com/swaywm/sway/pull/7178) needs to be applied to sway.~
(this works natively on sway versions >= 1.8)