Hacked mud

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Sending Virtual Inputs (Linux) ​

Roadmap ​

In this section of the guide we will learn how to send virtual key strokes to a hackmud window. Here's a rough roadmap of what we need to do:

  1. Extract the DISPLAY environment variable
  2. Find the X11 window ID using xdotool
  3. Use xdotool to send key presses and text

Requirements ​

Install these packages

bash
sudo apt install xdotool  # Debian/Ubuntu

Collecting the process info ​

First we need to collect some info about the hackmud processes

Get the PID if you haven't already

  • DISPLAY env variable - Display at which hackmud was launched at
  • WindowID - Window ID of a hackmud client

Using the PIDs we can find the DISPLAY variable that was used when the program started

bash
cat /proc/${PID}/environ | tr '\0' '\n' | grep DISPLAY
bash
username@hostname:~$ cat /proc/7738/environ | tr '\0' '\n' | grep DISPLAY
DISPLAY=:0
username@hostname:~$ cat /proc/137363/environ | tr '\0' '\n' | grep DISPLAY
DISPLAY=:95

Display 0 is a default display (aka desktop). Display 95 is virtual and invisible.

With the display variable we can find the window ID

bash
DISPLAY=:${N} xdotool search --classname hackmud_lin.x86_64
bash
username@hostname:~$ DISPLAY=:0 xdotool search --classname hackmud_lin.x86_64
65011720
username@hostname:~$ DISPLAY=:95 xdotool search --classname hackmud_lin.x86_64
39845894

Sending inputs ​

You now can use these 2 commands to send inputs to the game.

Use this to send text:

bash
DISPLAY=:${display} xdotool type --window ${windowId} --delay 0 "${escapedText}

Use this to send special keys like Enter and Escape:

bash
DISPLAY=:${display} xdotool key --window ${windowId} ${key}

And you can wrap them into methods to call anywhere in your code

ts
import { exec } from "child_process";
import { promisify } from "util";
const execAsync = promisify(exec);

export const keyNames = ["Return", "Escape"] as const;
export type KeyName = (typeof keyNames)[number];


export abstract class virtualKeyboard {
  static async sendTextToWindow(windowId: number, display: number, text: string): Promise<void> {
    const escapedText = text.replace(/"/g, '\\"');
    await execAsync(
      `DISPLAY=:${display} xdotool type --window ${windowId} --delay 0 "${escapedText}"`
    );
  }
  static async sendKeyToWindow(windowId: number, display: number, key: KeyName): Promise<void> {
    await execAsync(`DISPLAY=:${display} xdotool key --window ${windowId} ${key}`);
  }
}