Transfer From PC to PC Via USB Cable

[PiberiusWilde]

Just a simple question. I was just wondering, is it possible to transfer files from one PC to another just using a USB cable? Let's say as an example using a USB type A to C. Connecting to my desktop's USB A port and connecting the cable to my Laptop's type C port.

[Shimejii]

No. Ethernet to Ethernet could work. Or if you have a Homegroup and set that up with permitted devices.

[whispous]

Nope, USB does not support a Host only-to-Host only connection. PCs can only be hosts, unlike mobile devices like phones/tablets.

 

This is a question has has been around since the dawn of USB

[ieleja]

In Google: "connect computers usb", but better is stay with LAN2LAN option, this works without invest in strange cables and works out-of-the-box...

[mariushm]

There were USB transfer cables but they did not create a direct connection between computers. 

 

You can see those cables as a two separate usb to ethernet adapters, with a tiny ethernet cable between the two ethernet adapters. That's what's hidden in the nodule in the middle of such usb transfer cables. 

 

The easiest would be to use an ethernet cable between computers. If one of the cards is only 100 mbps, then you need a crossover cable (ethernet cable where the pairs of wires are in a different order in one of the connectors).  If both cards are gigabit, you could use a gigabit crossover cable (it's different than 100 mbps crossover cable) but a plain regular ethernet cable should also work because gigabit and higher ethernet cards are supposed to be smart enough to detect the order of the wires in the connectors.

Once connection is established, all you have to do is give each device a unique IP address (ex 192.168.100.1 and 192.168.100.2 ) and you can transfer data between computers.

 

[Mark Kaine]

so dumb question,  if i cant do that pc to pc, why can i do it phone to pc without any issues?  

 

what went wrong here? something must have gone horribly wrong here, also how can people accept this blunder?  

[Needfuldoer]

USB to USB direct connections don't work that way, but it can be done with special cables that have an interface in the middle.

 

https://web.laplink.com/cables/

 

You can also get two USB network adapters and connect them together with a regular Ethernet cable. Then you can just use regular network transfer systems (FTP, SMB, NFS, etc...)

[Mark Kaine]

1 hour ago, Needfuldoer said:

USB to USB direct connections don't work that way, but it can be done with special cables that have an interface in the middle.

 

https://web.laplink.com/cables/

 

You can also get two USB network adapters and connect them together with a regular Ethernet cable. Then you can just use regular network transfer systems (FTP, SMB, NFS, etc...)

again,  why does it work with phones then? must be some software limitation in windows to not allow usb transfers. 

 

it literally sees your phone as hard drive,  i see no reason why it couldn't see another pc as hard drive as well. 

[Needfuldoer]

8 minutes ago, Mark Kaine said:

again,  why does it work with phones then? must be some software limitation in windows to not allow usb transfers. 

 

it literally sees your phone as hard drive,  i see no reason why it couldn't see another pc as hard drive as well. 

USB works in a Host - Device model, not a peer-to-peer model. Phones universally support USB device mode, and sometimes USB host mode (or USB OTG). 

 

I don't know if the USB hardware in PCs supports USB device mode. Probably not, if it would make every other device connected to that USB controller stop working while that connection is in place.

[Mark Kaine]

6 minutes ago, Needfuldoer said:

USB works in a Host - Device model, not a peer-to-peer model. Phones universally support USB device mode, and sometimes USB host mode (or USB OTG). 

 

I don't know if the USB hardware in PCs supports USB device mode. Probably not, if it would make every other device connected to that USB controller stop working while that connection is in place.

ok, but thats still weird? when i connect my phone over usb, nothing stops working...

 

basically all you'd need is a "docking mode" or something then the pc would look like a hard drive for any other pc. 

 

ps: dont forget the phone actually asks which mode you want, transfer or read only (it still acts as a hard drive either way tho) 

[Needfuldoer]

6 minutes ago, Mark Kaine said:

ok, but thats still weird? when i connect my phone over usb, nothing stops working...

Because your PC is the Host, and your phone is in Device mode.

 

Your PC doesn't switch to Device mode. I don't know if the USB controllers in PCs even support running in Device mode.

[mariushm]

34 minutes ago, Mark Kaine said:

again,  why does it work with phones then? must be some software limitation in windows to not allow usb transfers. 

 

it literally sees your phone as hard drive,  i see no reason why it couldn't see another pc as hard drive as well. 

USB is designed in such a way that one end must be the Host and the other part must be a "Device" 

 

Only the Host controls communication , the host keeps asking the device "Do you have some new stuff to give me?" and the device has to wait for the Host to ask. 

 

Your phone can switch itself to either Host or to Device mode, computers don't do that .... when you connect the phone to your computer, the computer is the Host, and the phone shows up as a device, as in "mass storage"  or a camera or whatever. 

When you connect a keyboard or some other device to the phone's usb, it switches itself to Host and controls stuff. 

 

The two computers are both Hosts,  so that's why a usb cable between computers won't work, both will want to be Host.  

As I said, usb transfer cables work by having two devices in the middle of the cable : 

 

computer 1  (host) ------- --- [ device 1 ][ device 2 ] ------------- computer 2 (host)

 

Here's a picture from a usb cable teardown, you'll notice the two crystal oscillators, one for each device (both devices may be in a single plastic chip but there's two separate ones) : 

 

 

From specs / brochure of Prolific host-to-host bridge controller chip used : https://www.prolific.com.tw/US/ShowProduct.aspx?p_id=34&pcid=43

Note the "logic device" on each side of the chip and the "glue" between devices, each computer is a Host and sees the cable as a device. 

 

 

From 

 

 

[whispous]

18 minutes ago, Mark Kaine said:

ok, but thats still weird? when i connect my phone over usb, nothing stops working...

 

basically all you'd need is a "docking mode" or something then the pc would look like a hard drive for any other pc. 

 

ps: dont forget the phone actually asks which mode you want, transfer or read only (it still acts as a hard drive either way tho) 

Trust me: you do NOT want USB devices to have access to the filesystem on your computer.

[Nuzicx]

I believe Apple had a boot option to put your hdd in device mode to transfer your data over to your new machine via FireWire. This was 10 year ago last time I did this so not sure if it’s still supported with iCloud being a thing now and Time Machine.

[Kisai]

On 1/14/2024 at 10:01 PM, PiberiusWilde said:

Just a simple question. I was just wondering, is it possible to transfer files from one PC to another just using a USB cable? Let's say as an example using a USB type A to C. Connecting to my desktop's USB A port and connecting the cable to my Laptop's type C port.

 

No, because it's not designed for that. 

You need one of these:

https://www.amazon.ca/Laplink-SuperSpeed-Transfer-Cable-PCmover/dp/B071D4WYB9/

 

Or this

https://hackaday.com/2020/08/25/the-usb-null-modem-cable-is-now-a-thing/

 

Either way, we've come a long ways from the null modem cable where you plug two computers together with a 9-pin serial or a 25-pin parallel port cable. Even when you did this, you needed a software network adapter called "direct cable connection"

 

There is no mechanism to plug a cable into a computer and suddenly access the file system. That has to be done by the OS treating the connection as a network cable and network share.

 

What happens when you plug in devices like the iPhone and Android, is they show up as a "media storage device" which is done by emulating a "USB drive"