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General Software Architecture

Events

Each instance of lan-mouse can emit and receive events, where an event is either a mouse or keyboard event for now.

The general Architecture is shown in the following flow chart:

graph TD
    A[Wayland Backend] -->|WaylandEvent| D{Input}
    B[X11 Backend] -->|X11Event| D{Input}
    C[Windows Backend] -->|WindowsEvent| D{Input}
    D -->|Abstract Event| E[Emitter]
    E -->|Udp Event| F[Receiver]
    F -->|Abstract Event| G{Dispatcher}
    G -->|Wayland Event| H[Wayland Backend]
    G -->|X11 Event| I[X11 Backend]
    G -->|Windows Event| J[Windows Backend]
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Input

The input component is responsible for translating inputs from a given backend to a standardized format and passing them to the event emitter.

Emitter

The event emitter serializes events and sends them over the network to the correct client.

Receiver

The receiver receives events over the network and deserializes them into the standardized event format.

Dispatcher

The dispatcher component takes events from the event receiver and passes them to the correct backend corresponding to the type of client.

Requests

// TODO this currently works differently

Aside from events, requests can be sent via a simple protocol. For this, a simple tcp server is listening on the same port as the udp event receiver and accepts requests for connecting to a device or to request the keymap of a device.

sequenceDiagram
    Alice->>+Bob: Request Connection (secret)
    Bob-->>-Alice: Ack (Keyboard Layout)
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Problems

The general Idea is to have a bidirectional connection by default, meaning any connected device can not only receive events but also send events back.

This way when connecting e.g. a PC to a Laptop, either device can be used to control the other.

It needs to be ensured, that whenever a device is controlled the controlled device does not transmit the events back to the original sender. Otherwise events are multiplied and either one of the instances crashes.

To keep the implementation of input backends simple this needs to be handled on the server level.

Device State - Active and Inactive

To solve this problem, each device can be in exactly two states:

Either events are sent or received.

This ensures that

  • a) Events can never result in a feedback loop.
  • b) As soon as a virtual input enters another client, lan-mouse will stop receiving events, which ensures clients can only be controlled directly and not indirectly through other clients.