NextSync tab

The NextSync tab

In one line: send files from your PC to a real ZX Spectrum Next over Wi-Fi — and browse the Next's SD card from your desk.

This tab is for real hardware owners whose Next has an ESP Wi-Fi module (KS1, KS2 or a clone). No card removal, no card reader.

The way it works is worth understanding, because it explains most of the confusion new users hit: your PC is the server and the Next is the client. The app sits and waits; nothing happens until you type a .sync5 command on the Next itself. If you start the server and nothing seems to happen, that is why — the Next has to call in.

If you use an emulator rather than real hardware, you want the SD Card Utility tab instead.

Two modes

A pair of sub-tabs sits at the top of the page. They are two different ways of using the same connection, and the app reopens in whichever you used last.

Mode	What it is	Use it when
🔄 Classic sync	One-way folder sync, PC → Next. You pick a folder; everything in it is pushed to the Next, and later runs only send what changed.	You keep a "Next stuff" folder on your PC and want the Next to mirror it.
🗂 Remote Explorer	A two-pane file manager where the right pane is the Next's real SD card.	You want to poke around the Next's card, grab a file off it, or tidy up its folders.

Before you start: the dot command

Your Next needs a dot command in its /dot folder. The current one is .sync5, which speaks the faster, bidirectional Sync4 protocol. The older .sync still works for PC → Next only.

The first time you run it, the Next asks for the IP address of the machine running the server — the app prints the addresses to pick from in its log window. Because the Next connects in to your PC, your firewall must allow inbound connections on TCP port 2048.

📖 Full setup, IP configuration and building the dot from source: Installation → NextSync.

---

Classic sync

After Prepare: the log lists the IP addresses to type on your Next, warns that no syncignore.txt / syncpoint.dat exist yet, and reports how much is about to be sent. Sync mode and Slow transfer sit below it. (Hostname and IP addresses redacted; yours appear here.)

Quick start

1. Browse the file explorer to the folder you want to sync from.
2. Click Set current folder as new sync root folder and confirm. The box below now shows your sync root.
3. Pick a Sync mode on the right. For your first run choose Sync once, so the server stops by itself after one sync while you check things work.
4. Click Prepare Classic NextSync server and read the log window — it lists your PC's IP addresses and flags anything wrong.
5. Click ▶ Start Classic NextSync server.
6. On the Next, type .sync5 and press Enter.

Files transfer, and the log shows progress. Once the first full sync completes, a sync point file records what was sent, so later runs only transfer what actually changed.

The controls

Control	What it does
File explorer	Browse your PC. Navigating here does not change the sync root — that is a separate, deliberate action.
Sync root box	Shows the folder that will be synced. You can also type a path straight into it.
Set current folder as new sync root folder	Appears only while you are browsing somewhere other than the current sync root. Asks for confirmation.
Create / Delete SyncIgnore File	Manages syncignore.txt in the sync root — a list of file patterns to skip.
Delete SyncPoint File	Deletes syncpoint.dat, the record of what has already been sent. Delete it to force a full resend.

Sync mode

Mode	Behaviour
Sync changed files (continuous)	The default. Keeps listening; sends only new or changed files.
Sync once	Does a single sync, then stops the server. Best for your first run.
Always sync (send everything)	Keeps listening and resends every file each time, ignoring the sync point.

Slow transfer reduces the transfer rate. Turn it on if you get ESP or Wi-Fi errors on a weak connection — it is the equivalent of the -slow hint on the dot command (-default and -fast are the others).

---

Remote Explorer

This turns the log area into a two-pane file manager, with your PC on the left and the Next's actual SD card on the right:

[ your PC's files ]   ->:   :<-   [ your Next's files ]

Before the Next connects: the right-hand pane reads "waiting for .sync5 -listen". Run that command on the Next and it fills with the card's contents.

Quick start

1. Click the 🗂 Remote Explorer sub-tab.
2. Click ▶ Start Remote Explorer NextSync server. A pulsing green indicator confirms it is live.
3. On the Next, type .sync5 -listen (short form: .sync5 -l).

The right pane fills with the Next's current directory and stays connected until you stop it.

What you can do

• Transfer — select items and use ->: (PC → Next) or :<- (Next → PC), or drag and drop between the panes. You can drag straight in from your operating system's file manager too.
• Navigate — double-click folders; Up and Refresh on either pane.
• Manage — New Folder, Rename and Delete work on the Next's card as well as your PC.
• Right-click for more: Get size, Remote Zip / Remote Unzip file, and the usual Copy / Cut / Paste / Rename / Delete / Refresh.
• + Drive — the Next cannot reliably report which drives exist, so if you have storage the app hasn't found, add its drive letter here by hand.

Ending the session

Any of three ways:

• Click ⏹ Stop NextSync server in the app.
• Switch back to the 🔄 Classic sync sub-tab.
• Press BREAK (Caps Shift + Space) on the Next — its equivalent of Ctrl-C.

BREAK always lets an in-progress transfer finish first, so you never end up with a half-written file or folder.

Starting it automatically

Launch the app like this and the Remote Explorer opens with its server already running, using your saved sync root — so the Next only has to run .sync5 -listen:

python zx-next-unite.py -start-remote-explorer-listener

This affects that run only; your saved settings are untouched.

---

Sending files from the Next

The Sync4 protocol added the reverse direction. On the Next:

.sync5 -send <file or directory>

The file or folder is pushed back to your PC, into the sync root. What happens when the file already exists on your PC is up to you — set "NextSync — when a sent file or directory exists locally" in Settings to Prompt (the default), Overwrite or Ignore.

The HTTP bridge

Also in Settings: a small web server that republishes a running Remote Explorer session as plain HTTP routes, so a browser, curl, or another Next running the .http dot command can drive the connected Next's SD card. It needs the optional flask package.

⚠️ This is a LAN-only file server. Both the -listen protocol and the HTTP bridge on top of it are unencrypted, and unauthenticated by default — anyone who can reach the port can list, download, upload and delete files on your Next. Run it only on a network you trust and never expose the port to the internet. The Require bearer token option in Settings adds a basic gate against casual access on a shared LAN.

Troubleshooting

Nothing happens after I start the server. Expected — run .sync5 on the Next. The PC end only listens.

The Next can't reach my PC. Almost always a firewall blocking inbound TCP 2048. The log window lists the IP addresses to try.

ESP or Wi-Fi errors mid-transfer. Tick Slow transfer (or use -slow on the Next).

Timer messages in the console. Harmless; ignore them.

It syncs the wrong folder. Check the sync root box — browsing the explorer does not change it. Use Set current folder as new sync root folder.

Everything resends every time. You are in Always sync mode, or syncpoint.dat was deleted.

Still stuck? Try Jari Komppa's original command-line nextsync.py from the nextsync v1.2 release. ZX-Next-Unite shares its code base, so if that syncs, this should too.

---

See also: Installation → NextSync · HTTP bridge reference · SD Card Utility tab for emulator users.