Linux

Install Termux and run sshd -D -d -p <port>

If you want just a replacement for Warpinator, LocalSend is definitely the way to go. I used Warpinator before, and LocalSend is just an overall better version of the same thing imo. Finds other devices instantly, can also send text in addition to files and folders, and is available across platforms.

If it's anything big I send it to my synology nas. If it's something small then I honestly just send it through Signal. Although, I do wanna try this kde connect thing out as well.

Primitive ftpd from fdroid is my go-to "too lazy to configure a cloud thing" solution. It is fast and just works.

I have tried KDE connect, and it never works when I need it to. I just send it to myself on Signal. It's the easiest, most non-bullshit way.

I've been using FolderSync (Pro in my case) for many years to sync files (automatically and/or on-demand) from my phone to my Linux server.

kde connect is my recommendation also

You should try kde connect

Personally, I prefer LocalSend to KDEConnect.

Syncthing is great to periodically sync files between Linux and Android. And you could use it as file transfer service for occasional needs if you just share an empty directory.

uhm, well you can't primarily because android is a hot mess (quick note: this is mostly me ranting about the hell that android is for no fucking reason)

First of all, android only supports MDNS since android 12 and newer, MANY years after the standard was even finalized and put into use. (like a concerning amount) And yes, you can technically use that networking on a per app level (since android 6 or 8 i think), if it's implemented, but most apps don't because they're android apps. And the ones that do are basically useless (very cool thanks android)

Ignoring this, let's say that you have a samba server, and have a local DNS config setup to get around the MDNS bullshit. Oops, funny story, android doesn't natively support SMB shares, because apparently they aren't real and don't fucking exist. Now to be clear, most file managers do actually support SMB, the problem here is that those are often shit, and only supported in the actual file manager itself. If you wanted to per se, mount a samba share on android on the FS level, it is either impossible, or REQUIRES ROOT ACCESS.

Man it's a good thing rooting is easy, and not super convoluted, or risks bricking your phone in the event that it's designed like utter shit and cannot recover from being flashed incorrectly. (to be clear, i don't know shit about rooting, because it's a fucking disaster, and i might be misrepresenting it here, but only rooting, everything else is accurate)

so basically, cool story, the only option here that you have is using apps that are specifically designed to implement their own file transfer functionalities and protocols. There is one redeeming factor to this, and it's the fact that rsync exists, and that it isn't shit, but rsync isn't samba, so eat shit android. Rest in piss you disaster of an OS.

If by wirelessly you mean via Wi-Fi network then one convenient option is qrcp. It generates a QR-code right in your terminal, which you can scan with a phone and send/receive files through a web interface on the URL it provides.

If you want to transfer files regularly, there is another option. Almost every distro has Python installed, and the Python has a "built-in" FTP server. You need to just cd into desired directory and run the command python -m pyftpdlib -w. It will open a FTP server with root in this directory. You then can access it through a file manager, like Material Files for example, and send files and folders back and forth. In Material Files you can save the server address for future use.

SSH + Termux is one option. X-plore for Android is a good file manager with a bunch of options for transferring files over a network.

There might be more modern ways of doing this, but I run "Wifi FTP server" on my phone, with my download directory as its root. Then I use filezilla or whatever to transfer what I need. Trouble free and platform agnostic.

Haven't seen anyone recommend Flying Carpet, yet.

I use it to transfer files between my Windows desktop PC and my Steam Deck.

I use primitive ftpd on the phone and FileZilla on the PC.

For secure private transfer use the Warp flatpak in Linux and Worrmhole William in Android.

Simply install flatpak then install warpinator

I've been using SSHelper together with rsync for years and it works perfectly. You can log in the first time with a password, and place your public key to use key based auth going forward.

In addition to doing this over WiFi I also often use a usb to ethernet adapter (usb side plugged into phone) to get better performance if I'm doing larger transfers, for example copying off a large number of photos.

Edit: looks like there's a note on the play store page about incompatibility with newer Android versions. Disappointing. I guess I'll have to find another solution when I eventually upgrade my phone.

Server or desktop, and what types of files? I find that a self-hosted version of NextCloud does pretty well for keeping contacts, images, and videos in sync.

(You could run it on a Pi as an intermediary to both if desired)

I used to use stuff like AndFTP in the past for similar functions

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