Turn in: Issue's still here. Scrcpy v2.1

- [x] I have read the [FAQ](https://github.com/Genymobile/scrcpy/blob/master/FAQ.md).
- [x] I have searched in existing [issues](https://github.com/Genymobile/scrcpy/issues).

**Environment**
- OS: Linux Mint 20.2
- scrcpy version: 2.1
- installation method: Manual Build
- device model: LG K10 M250
- Android version: 7.0

**Describe the bug**
"Let's plug your phone in using this cable so you can talk to it wirelessly because Scrcpy can't look for a random port, it has to be 5555".
Updated scrcpy to v2.1.
Unfortunately this issue has been going on and is still a thing.
I find it inconvenient having to connect my phone via USB, so I can "enable" ADB to talk to it on port 5555; It defeats the purpose.

I did my research and was able to "get around" this by rooting my device and have it "free" another port, to which SCRCPY uses to connect to it. That works but it's not the end of the MAIN issue because it requires a rooted phone. Meaning I'm no longer able to transfer files by drag-and-drop, nor am I able to open all of my banking apps -- I literally have to restart my device so it becomes unrooted again -- so it's inconvenient because either I'm using Scrcpy or my essential apps.

@rom1v Is it possible to implement a method or function that enables scrcpy to reach my phone using any TCP ports available?
It's annoying leaving my device to charge and then having my terminal say "connection refused" every time I launch scrcpy.

The issue names no files or tests; start by tracing how scrcpy connects through ADB over TCP and where the fixed port 5555 assumption is applied. Define how an available port would be discovered or configured, then identify the tests needed to verify wireless connections without requiring a rooted device.

Written by the indexing model from the issue text.