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Comment by aendruk | Hacker News Reader

One thing I’ve always wondered is why it’s not common to be able to use a laptop as a generic keyboard and monitor for another computer. For doing maintenance on a headless machine it feels silly to go buy a keyboard and monitor when my laptop already is those.

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The GPD Pocket 3 has a KVM module that lets you do exactly this: it has HDMI & USB-C inputs and then it acts as a display, keyboard, and mouse for whatever machine it's connected to: https://gpd.hk/gpdpocket3

There's also the up-and-coming Minisforum V3 tablet that has a video input so that it can act as an external monitor, but I don't think it'll be able to share it's keyboard and mouse.

I agree with you, though, it really would be nice if this were a more common feature.

Not much of a hardware guy so don't know if this is at all plausible, but it'd be nice to see that as an extension port on the framework laptops.

That surely is the advantage of having modular ports. This is a fairly niche application so I can see why it's not a standard option, but for those who want it it could be a real game changer.

That’s a neat concept. Are there any products that take a video input and USB A connection, combine into USB C and act as a KVM?

I can’t even think what that would be called, TBH. It’s hard to search for.

Something like this maybe? Can use USB C or HDMI+USB A depending

https://www.amazon.com/Dopesplay-Wireless-Portable-Touchscre...

I've had some success searching "lapdock" as well, they're marketed towards using them with smartphones it looks like but can't see why you couldn't plug it into a server or computer as well.

I had one of those - not that exact one, it was great but I forgot it on the train one day.

The expansion ports on FW laptops are just backed by the same USB-C/TB4 ports you’d have on any other laptop. I don’t think the expansion form factor would make it any easier unfortunately

Oh no I didn't think it'd make things easier to implement, it's just that the need for a port is quite niche so it's unlikely you'd see it on many laptops, but if you have modular ports that justification is obviously far less a problem

But as I say, I don't know if a KVM module can be implemented over USB-C

It would be even better if Framework laptops could do that since they’re all about parts reuse.

Wow what a cool little piece of hardware! If it was just a bit smaller and had a radio for it, it would be an amazing phone

Seriously. A friend of mine built a cyberdeck specifically for this -- his mouse and keyboard can be switched to an external port and then cabled to another machine, and there are two HDMI ports on the side, one output and one input, with an internal switch to select either the deck's own machine, or the external input, as the source for the deck's monitor.

Has your friend done a write-up or parts list or build?

I think this would be a big hit on Hackaday or some similar site.

An OrangePi 5 Plus would be a good starting platform for this because of the HDMI input port.

Oooo.

what?? Can you run PiKVM on it?

I didn't know about PiKVM. I have no idea if it will run. Probably not as-is.

As someone who often deals with headless machines, the best solution I have found for using my laptop as a monitor is this: https://www.amazon.com/dp/B0BJ2YDV7Q It's basically a chip to capture the HDMI signal from a headless machine, and expose an emulated webcam via USB to your laptop. It's so tiny the electronic is basically built into the cable.

For the keyboard I haven't found a good solution other than buying a standard wireless keyboard (with integrated trackpad, for the rare cases where a mouse is needed).

For the keyboard I use a CH340+CH9329 cable, the former is a USB to UART converter and the latter is a UART to USB-HID converter. Feels unnecessarily complicated but hey at least it's only $3. It's effectively a USB "keyboard" controlled by another host.

Then I use a ~30 line Python script to forward key press to it. I really hope someone make a better integrated solution (or me having time to do it), though.

do you have a link to the cable you use, and what's your python script? Thanks!

That's basically what I do as well. I combined a similar HDMI dongle with a Logitech K400 Plus wireless keyboard+trackpad combo. It's an absolutely terrible membrane keyboard for everyday use, but having the trackpad and keyboard in the same device, using the same single dongle that has a storage slot in the keyboard makes things really easy for light, occasional use.

So if you have a broken monitor on your M1 with this can you use it on your other laptop? Because my broken M1 has a working keyboard.

Thats genius

The inability to simply connect one computer to another has always bothered me. Apparently there's a mode in USB 4 which will allow this.

There was a time when FireWire did that kind of thing -- not specifically with remote displays, but providing a high-bandwidth (for the time) wired network link between two PCs.

At home, in the Ye Olde 10/100 Ethernet days, sometimes I plugged my laptop into my desktop with 400Mbps FireWire to transfer big files.

No special cable required; any dumb FireWire cable with the right connectors on each end ("big" for the desktop, "little" for that particular laptop) worked just fine between any two FireWire devices.

You talking about Target Display Mode? Or did that never support FireWire?

I think Display Target Mode only worked with Thunderbolt, which was different.

I just used Firewire (er... maybe IEEE-1394, since it was in PC space) as a temporary and fast network connection for running (eg) IP stuff and file transfers with SMB, but it could have been used permanently.

At the time, plugging a Firewire cable in betwixt two Windows machines generated this network automatically, with RFC 3330 addresses for each end.

It just worked; each machine could be addressed by name nearly instantly after connection, and whatever file shares they had available could then be accessed with the same mechanisms that would be used on the normal Ethernet LAN.

I never did anything particularly complex with it.

That's how it works with USB too these days: https://news.ycombinator.com/item?id=39003469

TIL.

That's completely fantastic.

What was old is now new again.

One of the extremely rare cases where modern technology can actually do what was trivial decades ago.

Linus showed off a really impressive tech demo which accomplishes that: https://www.youtube.com/watch?v=GqCwLjhb4YY

I would link another source if I can, but there's almost nothing I could find about Thunderbolt Share.

RS232 null modem ftw!

At some point in college (in the mid 90s) I had a Linux box and a Sun box (pre-solaris) and had them connected up using X11 over SLIP over RS232 with a null modem and gender changer. The sun workstation could be completely controlled through RS232- you could reset the machine, do stuff to the boot system, etc. IIRC the max baud I could use was 19200, or maybe 38400.

> The sun workstation could be completely controlled through RS232

As a terminal right? the native function for RS232 was dumb terminals, and at some point that got abstracted a few thousand times to what we consider to be common terminals. You were running a proper paleo setup!

Ethernet has provided it all along.

https://en.wikipedia.org/wiki/Ethernet_crossover_cable

Yeah but then you're limited to Ethernet speeds, which (if even present on a modern laptop) is often 1/20th the speed of its fastest USB port. I just want to image the SSD without disassembling the laptop, damnit

Sure, but then you have to set ip addresses and network shares, it's a pain.

I just did this but had to buy a special tb4 cable. Just worked, though I had to look up the IP addresses.

hidclient will let your laptop pretend to be bluetooth keyboard and mouse.

https://web.archive.org/web/20180610141436/http://anselm.hof...

https://github.com/benizi/hidclient

Thanks for posting this. It is pretty much solving a major pain point for me (as is TFA, seemingly on a brief skim), even if with some usability friction.

I have a Flipper Zero and have always fantasized about having some sort of VMware/VirtualBox-like application that operates in a capture mode to forward all inputs to another device (similarly as to the guest machine in the VM player) with a keyboard shortcut to release the HIDs back to the host.

In the Flipper Zero's case (or any SBC/SOC/microcontroller/whatever-term-is-appropriate), it would be so lovely to be able to operate in all four combinations of:

Host - BT - Flipper - BT - Second device

Host - USB - Flipper - BT - Second device

Host - BT - Flipper - USB - Second device

Host - USB/GPIO - Flipper - USB/GPIO - Second device

Unfortunately, I don't work so close to the hardware, so I've no idea where to even begin with this. A man can dream. Sigh.

My laptop's monitor went bust and now serves as a glorified CPU.

Costs, extremely low demand, no standard interconnect and interfaces, anything non-standard wouldn't work with dead OS, costs.

Can’t it all be acccomplished in Software with usb-c?

You still need software support for it on the host device.

While you can imitate Keyboard and Mouse (and they would work through boot or without OS), Video is out of question for now.

And while there is still some value on it using on a healthy system, most of the time KVM device is needed when something is not working.

NB there is/was Intel ATM which provides (at least on paper and on rare, extremely rare posts on Internet) KVM-like experience and power control. Theoretically it can be used as the basis for single USB port KVM interface.

Thanks!

Oh me too, but that's now quite a few years ago. These days we have IPMI, no?

You can deduce the answer by charitably interpreting that the situations in which I’m attaching a keyboard and monitor are those in which that’s a reasonable action.

Everyone uses ssh to do that.

And what do you do when your ssh server stops working, or there's a hardware fault, a network fault, a failed OS upgrade?

Idk about all machines ever, but I remember being able to access ssh over a serial port.

Though in that specific case for me, it was more of a necessity rather than just a quirky way of using ssh (due to the “machine” just being a dev board with a UART ESP32).

To access the serial port remotely you need to add hardware to bridge it to the network. Or you go up to the machine and plug in another computer with a keyboard and monitor to access it directly.

That's a completely different use-case. SSH doesn't let me control the GUI on the remote

And no, X11 forwarding is not what I mean either

There is/was a tool called x2x, which somehow let you send your input (mouse/keyboard) to another machine (I think via X forwarding tricks, although I don’t know how it worked, so I could be wrong).

I tried it around a decade ago and at the time it felt a bit abandoned. I vaguely remember that it might not have worked with every window manager? Anyway, I assume it hasn’t got better supported since then. But it did feel magical.

x2x worked fine for input devices.

Later, things like x2vnc made the idea more cross-platform (X on the local unix-like box, VNC on some other platform), but only with two machines.

After that, Synergy became a thing, and supported many machines, but then they eventually went to a model that tended to require payment.

Later, Barrier forked from Synergy, and it allows much of the same functionality. It's still very free, and it still works, but it's kind of abandoned.

Today, there's Input Leap. It is (naturally) a fork of Barrier, and it is still sees regular development.

https://github.com/input-leap/input-leap

So, you'll accept any solution, except the existing ones that work?

XDMCP solves this exact issue. You use one device which becomes virtually an attached terminal of another device which is actually headless and with no input devices of its own. We've had this for 30+ years.

No, we already use the solutions that actually work, and are speculating why there isn't one with the simple, obvious user experience. Why shouldn't we?

> XDMCP

muh wayland

I'm sure we'll see functionality like that in Wayland.... In a decade or 2.

…except for when they can’t. The relevant retort would be that I could instead be using hardware with a remote management interface like IPMI, and building a custom OS installation image with remote access preconfigured. But even then I’m not sure how you’d have me troubleshoot surprise network issues.

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