Sending commands from computer via ethernet

I am planning on sending an input from a computer over ethernet to an Arduino equipped with an ethernet shield.

The main goal of this is when a key is pressed (say, "w" for instance), the computer will send a command to an Arduino, which will in turn send a command to a speed controller over PWM to turn on an RC motor.

For testing purposes, I can just have it blink an LED or something simple when the key is pressed. The pwm stuff shouldn't be too hard.

How would I even go about sending commands via ethernet? Write a HTML document? Website? Skip ethernet all together and go serial?

I have never made a project where I communicate input from a computer to an Arduino...

Thanks!

I am planning on sending an input from a computer over ethernet to an Arduino equipped with an ethernet shield.

How? What role (client or server) is the Arduino playing?

Skip ethernet all together and go serial?

That would be far simpler.

You can use UDP to send string via ethernet/wifi.
You'd need an app on your desktop to send UDP to your arduino.

Look at the UPD examples that comes with the Arduino IDE.

you can use serial off course. It's up to you.

If I send commands using serial, is there a way for it to automatically send the command once the key is pressed?

For the other tutorials I've seen, you have to press the send button first. Since this is a robot, I would want the communication to be instantaneous.

Serial Monitor requires you to click the send button or press the key.

Other terminal programs (e.g. realterm or putty) can / will send when you press a key.

Other advantage if not using serial monitor is that once your Arduino application is ready, you don’t have to start the IDE for communication.