6 ms·

Transfer files over an Ethernet patch cable

199 points by jllyhill 1mo ago

lstodd 1mo ago
I remember we played warcraft 2 over ~15m of cat3 cable stretched outside between two flats on 6th floor. Those were the times, lol.
- bronlund 1mo ago
  I remember playing over a 9-pin RS232 null cable - but I guess that is telling about my age :D Not Warcraft though - some ancient DOS game.
  - croon 1mo ago
    I believe the first Command & Conquer was the one I played that way. But I'm young, so it can't possibly be the same, can it?
    - doublerabbit 1mo ago
      The original CnC allowed you to play 1v1 via telephone number. Being 15, that was absolute wizardry. It would still works today if both parties have a landline.
      - me-vs-cat 1mo ago
        Landline? I don't understand. If both parties have a LAN line, shouldn't they use that to communicate?
  - Hikikomori 1mo ago
    Played Doom over null cable at home.
  - inigyou 1mo ago
    Before the world standardized on Ethernet/IP, Microsoft had an abstraction layer called DirectPlay. ("Direct" was that era's "Copilot" word for Microsoft)
    - pezezin 1mo ago
      FYI, EtherNet/IP is an industrial control protocol, not TCP/IP over Ethernet. Yes, that is the real name of the protocol, a more confusing name could not have been chosen... https://en.wikipedia.org/wiki/EtherNet/IP https://en.wikipedia.org/wiki/EtherNet/IP
      - inigyou 1mo ago
        FYI, IP is a phonetic acronym for "I pee", meaning "I urinate" Two letters can have more than one meaning!
        pezezin 1mo ago
        Yeah, and it can also mean Intellectual Property. But "Ethernet/IP" is not just "two letters", is a trademarked brand.
        inigyou 1mo ago
        I think the holders of the trademark of Ethernet might have something to say about that.
        pezezin 1mo ago
        Ok, you can go to the ODVA and tell them. https://www.odva.org/technology-standards/key-technologies/ethernet-ip/ https://www.odva.org/technology-standards/key-technologies/e...
      - idiotsecant 1mo ago
        I use E/IP all the time and if i had a nickel for every time i had to explain this to people I wouldnt have to use E/IP anymore.
- ButlerianJihad 1mo ago
  For anyone today who's got copper wire stretched between any buildings, you are in danger and your configuration is quite unwise. For every standalone building that has a ground, that building also has an electrical potential. This potential is not necessarily the same between two neighboring buildings. When you stretch a copper line between them, you are tempting fate, electrically, not to mention the dangers of lightning strikes and the elements attacking that connection. It is generally recognized that fiber optics are not only very efficient and durable, but also impervious to electrical troubles of the type that may plague inter-building connections. Simply grab switches or routers that support at least one fiber-optic connection, and link up!
  - lstodd 1mo ago
    Who cared, we were 15 at the time. Besides you worry too much. Entire cities were wired with cat5 hanged off steel cable between 9 to 15 story buildings in early 2000s, before fiber. Nothing burned down.
    - inigyou 1mo ago
      If your cable is shielded it's liable to spark and trip breakers. Happened to me when one building was horribly miswired (someone swapped live and ground somewhere) and fried part of my computer before the breaker tripped. In the worst case there isn't actually any breaker in the path (they are only on live wires and the worry here is ground loops) so your cable just melts. That didn't happen to me. Unshielded cable is theoretically isolated at both ends but who actually knows with some chinesium equipment?
  - EvanAnderson 1mo ago
    I did work for a small community college back in the 90s that had expanded their building multiple times since the 70s. The electrical potential between different parts of the building was significant enough to make wired Ethernet unreliable. (I never did understand why this was-- multiple electric service entrances with separate grounds, I assume.) Because of this they were an early adopter of fiber-based networking. I remember being wowed by ATM over fiber running between closets at a blazing 155Mbps (with tons of 10BASE-T clients connected to FORE chassis switches).
- sgt 1mo ago
  When I did LAN parties we had 10base2 over thin coax. Terminators at each end. Of course it was unstable because people kept disconnecting and everyone lost connection.
riobard 1mo ago
For the time spent finding the ethernet adapter, plugging the cable, configuring IP addresses, and testing with pings, any decent portable SSD drives should have finished copying tens of GB of data.
- yjftsjthsd-h 1mo ago
  As the article says, > Removable storage is quite slow unless you are willing to spend a lot of money. An SSD good enough to copy tens of GB quickly is not cheap.
  - riobard 1mo ago
    At this particular point in time, yes SSD is expensive. But 5~10Gbps USB 3.0 SSD had been very affordable for a long time before 2025.
    - debugnik 1mo ago
      Unluckily for us, and the author at the time of writing, we're in 2026.
      - Dylan16807 1mo ago
        You can still get a drive that will beat the ethernet connection by a lot for $50. But also I'd feel weird if I didn't have at least one good flash drive somewhere, so anyone like me would already have it. I'm going to ignore the part where the USB port described in the article sounds broken. A 100% functioning cable, especially a short one for a drive, is not hard to find.
      - riobard 1mo ago
        If you haven't yet got any portable drives in the drawer, chances are high that you rarely need to copy large amount of files around anyway. In which case free tier of cloud sync services would be preferred for the majority of users.
steve1977 1mo ago
People discovering that network cables can be used to network things. And then calling it a "trick" (I'm surprised it's not a "hack" actually).
- alnwlsn 1mo ago
  There is always some young person or new to the field learning for the first time. Post like this are exactly how I learned.
- concerned_user 1mo ago
  Back in the day you needed a modified cable for this with RX/TX swapped on one end but nowadays probably all nic chips have auto-detect so you can take a normal patch cable and do it.
  - bronlund 1mo ago
    Yeah, I remember those. When setting up an ad-hoc network, you were like; "where the eff is the crossover cable!" :D
    - luz666 1mo ago
      it was the red one, right?
      - bronlund 1mo ago
        Mine was just a custom made gray one, but I have seen those red ones, yes :D
        Ekaros 1mo ago
        I bought bunch of ready made 10 meter cables for lan party dunno 15 or 20 years ago... Used with switch... Grey with nice paper label at end with "Cross over"... Haven't had any issues with them ever in regular use... So pointless even back then...
nkurz 1mo ago
It would be nice if this article defined a "ethernet patch cable". I think he's just using "patch" as a slang term for a short cable and it actually works with any length of standard cable, but I'm not certain. Traditionally (pre-2000?), one had to use a special "crossover cable" to do direct connections like this, but apparently modern Gigabit ethernet adapters are able to detect this situation automatically?
- bronlund 1mo ago
  The way I learned this, is that patch cables use stranded wires, but ethernet cables use solid wires.
  - globular-toast 1mo ago
    They are all just twisted pair cables, probably Cat5e or Cat6 etc. The solid ones are usually used for structured cabling, inside walls and trunking, that doesn't often move. Structured cabling is terminated into keystones or patch panels, the "female" end. Patch cables are outside of walls and designed to be moved around and plugged and replugged. They are terminated with 8p8c "male" connectors, commonly called rj45. Stranded cable is used because it's much more flexible.
    - TorKlingberg 1mo ago
      This is the same for mains power cables. Permanent installs are usually solid cores, while the "flexi" cables you plug into a socket are stranded.
      - globular-toast 1mo ago
        Yep, up to a certain point. Thicker wires like 6mm^2 are stranded again, but the strands are very thick and few.
- lstodd 1mo ago
  IIRC crossovers are pre-2000, yes. "Fast Ethernet" or 100Base-T adapters usually could talk over straight link. edit: as for length, it depends. you won't get a gigabit over 150m of crap cat3, but you will get a link, even if it's 10 half-duplex.
ButlerianJihad 1mo ago
It seems a strange choice, for the demo and for the script, to manually configure addresses on both ends. If your TCP/IP stack is functioning properly, this will not be necessary. Once DHCP fails, you should get a pair of 169.254.0.0/16 (APIPA) addresses, and then Bob's your uncle. Configuring all this manually adds extra complexity when it seems that the goal is simply to connect up your cable and let 'er fly.
- rmunn 1mo ago
  Back in my college days, 169.254.x.y addresses were the bane of my existence, because my job was getting students' computers set up with the brand-new Ethernet connection in their dorm room. This usually required a tech to come out to their room and configure Windows 95 properly, with IP and DHCP instead of Novell Netware and IPX (I don't remember why Netware/IPX was the default on so many Windows 95 installs, but that was definitely what I found most often when I went to look at someone's computer that "wasn't connecting to the Internet".) Occasionally we had someone who knew what they were doing and had their Windows 95 settings set up correctly, and then all we had to do was activate their room's Ethernet port and add their MAC address to the DHCP server's list of authorized MACs. But most often I or one of the other techs had to head down to the person's dorm room and set up their computer's network settings correctly before it would work. Once the 169.254 address was replaced by 192.168, my job was finally done. But there were times when that took some doing.
  - kjs3 1mo ago
    I don't remember why Netware/IPX was the default on so many Windows 95 installs Because Quake multiplayer originally used IPX, not TCP. At least, that's why I had IPX loaded...
- ma2kx 1mo ago
  And if you prefer ipv6 you can as well just ping -6 ff02::1%eth0 (or eno1 or whatever your devices name in the particular subnet is) and receive all fe80 addresses of other hosts in the subnet. Also, why is he talking about "ethernet"? Its the IP layer, not the ethernet layer...
- 1mo ago
yjftsjthsd-h 1mo ago
I am 95% confident you don't actually need to assign IPs. Do this: # ping all link-local devices on an interface: ping ff02::1%eth0 And then do your socat/rsync/whatever to the only IP that responds.
- steve1977 1mo ago
  I would assume so as well, I'm not sure if all host operating systems act the same though. But you could probably just wait a couple of seconds and the interfaces would have assigned themselves link-local addresses.
  - QuantumNomad_ 1mo ago
    > I'm not sure if all host operating systems act the same though I have two USB-C Ethernet adapters laying around that I bought some time ago. I connected one of them to a Linux machine and the other to my MacBook Pro and experimented a little bit. All of the following commands and outputs are from the MacBook Pro. The USB-C Ethernet interface is en8. On the macOS side, I can see that a 169.254.xx.xxx/16 IPv4 address has been assigned by macOS as there is no DHCP running on the link, and it has an fe80::xxxx:xxxx:xxxx:xxxx%en8/64 IPv6 address assigned by macOS as well. (The x-es in the aforementioned IPv4 and IPv6 addresses were put there by me in this text. On the system they are decimal and hexadecimal digits in the IPv4 and IPv6 addresses respectively.) The first attempts, relating to ssh, maybe would not work on any system anyway? Not sure how the ff02 multicast prefix for link-local scope works exactly and what its limitations are. % ssh ff02::1%en8 ssh: connect to host ff02::1%en8 port 22: Address family not supported by protocol family % ssh -6 ff02::1%en8 ssh: connect to host ff02::1%en8 port 22: Address family not supported by protocol family % ssh -B en8 -6 ff02::1%en8 ssh: connect to host ff02::1%en8 port 22: Address family not supported by protocol family % ssh -B en8 -6 ff02::1 ssh: connect to host ff02::1 port 22: Address family not supported by protocol family Trying ping: % ping ff02::1%en8 ping: cannot resolve ff02::1%en8: Unknown host I then tried a couple more variations with ping similar to the variations I did with ssh, before moving on to ping6. Seems that the ping command on macOS is IPv4 only. I don't see any -6 flag for the ping command in the man page on macOS. But there is the ping6 command for IPv6, which I have used before (just not with ff02 addresses). Finally, ping6: % ping6 ff02::1%en8 PING6(56=40+8+8 bytes) fe80::xxxx:xxxx:xxxx:xxxx%en8 --> ff02::1%en8 16 bytes from fe80::xxxx:xxxx:xxxx:xxxx%en8, icmp_seq=0 hlim=64 time=10.893 ms 16 bytes from fe80::yyy:yyy:yyyy:yyyy%en8, icmp_seq=0 hlim=64 time=14.365 ms 16 bytes from fe80::xxxx:xxxx:xxxx:xxxx%en8, icmp_seq=1 hlim=64 time=0.511 ms 16 bytes from fe80::yyy:yyy:yyyy:yyyy%en8, icmp_seq=1 hlim=64 time=2.467 ms 16 bytes from fe80::xxxx:xxxx:xxxx:xxxx%en8, icmp_seq=2 hlim=64 time=0.440 ms 16 bytes from fe80::yyy:yyy:yyyy:yyyy%en8, icmp_seq=2 hlim=64 time=2.393 ms ^C --- ff02::1%en8 ping6 statistics --- 3 packets transmitted, 3 packets received, +3 duplicates, 0.0% packet loss round-trip min/avg/max/std-dev = 0.440/5.178/14.365/5.422 ms Worthy of note is that when I ping6 ff02::1%en8, I get responses from both side of the connection (the ones I substituted with fe80::xxxx:xxxx:xxxx:xxxx%en8 are the same IPv6 address that I see for the en8 interface in ifconfig output on my MacBook Pro, and the ones I substituted with fe80::yyy:yyy:yyyy:yyyy%en8 are the IPv6 address of the other end of the link-local connection). Attempting to ssh to the IPv6 address from the ping6 output, making sure to pick the one that is not the IPv6 address of the ethernet interface that is connected on the MacBook Pro side itself: ssh fe80::yyy:yyy:yyyy:yyyy%en8 Output of that I will omit for brevity, but it is the standard question about accepting the ssh fingerprint of the machine and letting me know that this fingerprint is previously known by another name, as I have previously ssh'd into that machine from this one but using the .local mDNS hostname rather than this fe80 IPv6 address. So it seems that having ping6 ff02::1%en8 up the sleeve is useful indeed on macOS too, as long as one knows to use ping6 and not just ping, and that attempting to ssh to ff02::1%en8 does not work directly from macOS at least not for me.
yitchelle 1mo ago
This remind myself the good old 8bit days of using a cross-over RS232 cable to send a file from one computer to another. even at 30bps, it was much more reliable than write my data to a cassette tape on one computer and then reading on the other.
- ErroneousBosh 1mo ago
  I have plugged two ZX Spectrums together and done LOAD "" on one and SAVE "THING" on the other to transfer data. If you get away from BASIC commands and copy the tape routines up into RAM you can mess with the timing values, and with care you can get it from an average of 1800bps up to around IIRC 12000bps before things really fall apart. Probably with better interfacing you'd get even faster. With more conservative values, this is how "speedloaders" worked. In the late 80s or early 90s one publisher released games on CD where it would load in the loader at normal rate then ramp up to some unholy speed that CD had the bandwidth and stability for but tape did not.
- hdgvhicv 1mo ago
  232 crossover was still going in the PC era with laplink. Parallel was an option too if I remember. Used to play Duke Nukem 3D over a null modem serial cable. In the days of the spectrum where you loaded via an analog audio input from a tape, and saved via the output, you could move from one to another in the same way, skipping the tape. Apparently this was about 1kbit per second.
- inigyou 1mo ago
  But did you ever plug one computer's cassette out directly to another computer's cassette in?
  - yitchelle 1mo ago
    Not possible on my system. It was only computer<->cassette connection.
    - inigyou 1mo ago
rmunn 1mo ago
That used to require a crossover cable; I've done precisely that (with a crossover cable) back before https://en.wikipedia.org/wiki/Medium-dependent_interface#Automatic_MDI-X https://en.wikipedia.org/wiki/Medium-dependent_interface#Aut... became widespread. With a straight-through cable, you'd be connecting the Transmit (TX) pin of one adapter to the TX pin of the other one, and the Receive (RX) pin of one to the RX pin of the other — and neither device would "hear" the messages the other one was sending. A crossover cable flipped those wires, so each device's TX pin was connected to the RX pin on the other end, and both devices could "hear" each other. But with auto MDI-X, each device would notice "hey, I'm sending but not receiving anything," and would try flipping its Transmit and Receive functions around (transmitting on the RX pin and receiving on the TX pin). Since each device waited a random period before doing that, it was very unlikely (nigh-impossible) that they would both flip at the exact same moment. And if they did, the second interval would most likely not be identical either. I'm simplifying a bit in the explanation above, but that's the broad strokes. And that's how my carefully-labeled crossover cables started gathering dust. (And then I realized "hey wait, I can just use these as normal cables now", and pulled them back out of storage and mixed them with my normal patch cables).
- soundworlds 1mo ago
  That wasn't that long ago was it..? /looks longingly out the window, and catch my aging face in the reflection
  - abrookewood 1mo ago
    Yup ... still have some old 'xover' cables lying around - all of which are RED in colour to explicitly declare their usage
    - valleyer 1mo ago
      Interesting. I don't remember my crossover cables being marked that way; you had to read the dot-matrix printing along the side to know. Color would have been way more handy.
3r7j6qzi9jvnve 1mo ago
tbstream looks fun, but hard to use for the casual user -- not sure if it'll get simpler but I don't think I'll remember messing in configfs just to transfer a file: https://git.kernel.org/pub/scm/linux/kernel/git/westeri/thunderbolt.git/commit/?id=6db21d817b43f8ce5654ccc7aff80d40e4dba4ac https://git.kernel.org/pub/scm/linux/kernel/git/westeri/thun...
ltbarcly3 1mo ago
Ok is there a version for usb-c? Because that would be 10x or more faster and I have a usb-c port and a usb-c cable at all times.
- Ballas 1mo ago
  If one of the devices support DRD (OTG), but unless one of them is an ARM device, chances are slim.
  - xuhu 1mo ago
    Could a smartphone sit between 2 regular laptops to achieve this with 3 USB cables and a hub ?
    - rcxdude 1mo ago
      You would need a USB hub that could turn a USB device into two USB device ports, which I don't think exists. (hubs are essentially only a host-side thing).
  - rcxdude 1mo ago
    With USB-C this is a lot more likely, the main issue is going to be software support (Decent chance you could hack something up if one of the devices is running linux. No idea if anything exists for windows).
- kotaKat 1mo ago
  https://www.amazon.com/Hagibis-Ethernet-Portable-Thunderbolt-Compatible/dp/B0FC1HSS9X https://www.amazon.com/Hagibis-Ethernet-Portable-Thunderbolt... Carry a couple USB-C to RJ-45 dongles ;)
  - johnwalkr 1mo ago
    What a clever idea. I carry an ethernet dongle but this one is just the male end and a female usb-c port, meaning your existing usb-c cable is useful and you don't need to carry an ethernet cable.
superdisk 1mo ago
I used to do this to play Minecraft with my cousin without a router.
Yannik_Sc 1mo ago
The USB/Thunderbolt one is a nice catch and good to know if you want to move you data to a new PC. Dell XPS (with soldered SSD) to Framework move just took a few minutes by dd'ing through the created network interfaces (it's different from the tbstream). The limiting factor was the Dell's SSD actually.
- johnwalkr 1mo ago
  I've been doing this for years between MacBooks with a thunderbolt 4 cable. It's very fast and unlike 10Gbps ethernet, doesn't require a bulky, power-hungry[1] adapter. MacOS also will use thunderbolt automatically for Migration Assistant if available. [1]Most people don't realise how much power ethernet consumes. Even 100Mbps ethernet consumes about 0.5W per port and it goes up with higher speeds.
  - drnick1 1mo ago
    Indeed, 10Gbps cards and adapters run very hot. I placed an 80mm right under the card in a PCI fan mount to keep the expansion card cool. The fan does not need to spin fast, but some directed airflow seems absolutely necessary.
pcblues 1mo ago
Yup. "Computer to computer should not be seen without a device in between (unless playing ROTT with your housemates)" 35 years ago maybe :) I had serial and parallel socket, and routerless networking happening on my home systems :) Use cases? Emergencies and maybe dedicated backup.
SillyUsername 1mo ago
You can also pipe it through zstd on the fly, for data that compresses well you'll often see 1.5 to 3× the raw throughput, so a gigabit link can effectively move 165–330MB/s. Receiver: socat -u TCP6-LISTEN:1234,reuseaddr STDOUT | zstd -d -c | tar -xpf - -C /destination Sender: tar -C /source -cf - directory | zstd -T0 -6 -c | socat -u STDIN 'TCP6:[fd42:dead:beef::2]:1234' -T0 uses all cores. Bump the level above -6 for more compression, drop it for more speed, but if your CPU can't keep up, high levels will actually slow it down. Already compressed data won't see much benefit.
- ElectricalUnion 1mo ago
  If you're using specifically zstd, on the sender side, instead of tweaking the whole tunnel once, you can use --adapt to dynamically adjust to i/o conditions.
- effdee 1mo ago
  Btw, tar(1) on MacOS shows the file currently being processed when you hit Ctrl-T (i.e. when it receives SIGINFO). And talking about signals, dd(1) can show the amount of data it has processed as well as the throughput. The signal depends on the implementation(e.g. SIGINFO for MacOS, SIGUSR1 for GNU).
awruko 1mo ago
I literally had to cross over the cable once. It was some sort of demo and the cross over cable was missing. The local computer stores didn’t have one and under the time pressure … I have used the pocket knife and convert the cable. It was before 2000 so the speed was limited to 10/100 Mbit - ifconfig did’t report errors and demo went smooth.
sgt 1mo ago
Even easier on macOS. Something like this should work: ifconfig enX inet6 fd42:dead:beef::1 prefixlen 48 No ned to bring it up as it should already be up. enX should be your USB/thunderbolt ethernet adapter, e.g. en6. Then you can go ahead and transfer with socat to your other machine, even if it's a Linux machine. I tend to use nc but socat will definitely be faster. Why the deadbeef network one might wonder? It's private space so won't conflict with public addresses. That being said though, in 99% cases of big files I'll just airdrop the files!
- Steltek 1mo ago
  ifconfig still probably works on Linux too but it's discouraged because, frankly, it sucks compared to ipconfig2. Most of macOS' CLI feels old and crusty. Which makes sense when you realize it's a fossilized niche BSD from the early 00's.
  - sgt 1mo ago
    ifconfig(8) is meant for low level stuff. What Linux did was replace ifconfig with another low level (e.g. ipconfig2), which makes more sense there I suppose. But don't get the impression that ifconfig is the easiest way in macOS on the CLI, it's networksetup(8).
- ButlerianJihad 1mo ago
  It seems quite strange to me that hackers have adopted "0xdeadbeef" as some sort of generic hex string to use in production. AFAIK, "0xDEADBEEF" originated as a "magic number" in systems like IBM RS/6000 and Solaris, and it was a red-flag number! It meant something in your system was wrong and you'd better check it out! https://en.wikipedia.org/wiki/Magic_number_(programming)#Debug_value https://en.wikipedia.org/wiki/Magic_number_(programming)#Deb... Surely there are more pleasant, vegan hex strings to use, if you want to indicate an ephemeral IPv6 address?
  - picofarad 1mo ago
    CAFEBABE? Sexist, so thats out. FACEB00C? In use. Darn this is hard.
brandolini10x 1mo ago
I wonder how we managed to invent the Internet before this trick. Next week's front page will be "Amazing trick: connect two wheels with a platform and you can ride instead of walk"
theodric 1mo ago
"Plug two computers into each other with a network cable and staticly configure the IP addresses" should not be a novel or notable enough idea to trend on HN! This is boggling.
- federiconafria 1mo ago
  I thought what made the article special was the use of a "patch" cable but the network cards should be able to negotiate anyway, I was very confused about what was the notable thing.
  - theodric 1mo ago
    Auto-MDI/X (auto-crossover) was codified in IEEE 802.3ab-1999, the specifcation for gigE, 27 years ago
    - a96 1mo ago
      And it's even been supported really well for almost as long.
1vuio0pswjnm7 1mo ago
"I think it's underappreciated for non-internet applications and doesn't even need a local network: point to point wiring is perfectly fine." In the 1990s I used crossover cable for years with Apple computers that I bought for music production To keep the disk drives "clean", I never connected these computers to the internet If I needed to transfer files to or from Apple computers I connected them to a laptop with crossover cable I grew up using Apple computers that had no internet connection at home and school so this seemed perfectly natural I used computers running Windows 3.11 that had no internet connection, only LAN Needless to say, "Big Tech" companies like Apple are not what they used to be These companies don't really produce anything to be used "offline" anymore. Watching the default network traffic from "Big Tech" marketed computers and software is sad Not automatically trying to phone home is bad for the "business" of data collection, surveillance and ad services There used to be a different attitude toward the internet; there was less trust. I can still find traces of this in the archives at textfiles.com
slipperybeluga 1mo ago
[dead]
yonatan8070 1mo ago
My usual method for this is to spin up a small webserver using the built-in Python module: python -m http.server Then just wget the file I need from the other system.
- bitpush 1mo ago
  But that requires both the machines to be on a network right? I believe what OP is demonstrating two (isolated) machines talking to each other.
  - yonatan8070 1mo ago
    It works just as well if they're on a direct link as demonstrated in the OP, as long as there's working IP connectivity. This isn't to say the way it's done in the OP is wrong, socat is also great, and you can also compress them on the fly by piping through zstd as others mentioned in this thread.
    - bitpush 1mo ago
      Apologies if this is obvious but I'm not following it. > as long as there's working IP connectivity. Dont you need to be on a network to get 'IPs'. It is usually a router's job to setup the network, and also provision IPs. Two devices, not connected to a LAN has nothing. No IP, except 127.0.0.1 and localhost. So then, how do you talk to another device. There isnt an address. OP's article is essentially setting up a P2P connection when there's no third party (router)
      - zamadatix 1mo ago
        Two devices connected to each other are just another form of LAN - one with 2 nodes instead of many. You can manually configure IPs without a router exactly as this article demonstrates: # On sender... ip address add dev eth0 fd42:dead:beef::1/48 ip link set dev eth0 up # On receiver... ip address add dev eth0 fd42:dead:beef::2/48 ip link set dev eth0 up The first 2 lines are run on one host and the second two lines on the second host. The 1st line of each segment sets the IPv6 address to use and the second line of each segment makes the adapter enabled. Plug an ethernet cable in and they can reach each other. As to why, just think of it as "the same way the computer would figure out how to send a packet to the gateway, just to another client in the network segment instead" You only need a router set up to go to a different subnet. If both hosts are in the same subnet then it's just a neighbor resolution (well, you can do neighbor discovery manually too if you really want... but, since it's automatic, no reason too) followed by ethernet bridging. Two hosts with nothing else just plugged into each other should actually already have assigned themselves IPs you could use for this though. They are known as IPv6's link local addresses and are explicitly meant for communication on the local subnet. Ethernet & IP are fun abstractions to really get into the weeds about. When it comes to running networks it's actually a bit of a fight to try to make sure only the addresses the router allows can be used! A whole bevy of technologies address that for the different protocols.
throwaway67743 1mo ago
But... link local precludes the need to configure addressing, even without v6, broadcast ethernet frames exist... why do people keep posting dumb solutions to already solved problems?
doublerabbit 1mo ago
Next up, token ring networks. Remove one cable and the network falls flat, or I thinking of another topology? I do wonder sometimes how the world would be operating if IPX was the primary ethernet. I never got to play with it.
constantlm 1mo ago
If this doesn't work, you could always try Laplink with a parallel cable
icar 1mo ago
I remember doing this at uni, networking labs
snvzz 1mo ago
>over an Ethernet patch cable Was I alone in expecting it to be used in an unconventional way? Like, MAC level with not a trace of TCP/IP, or not even Ethernet but, say, uart over the wire. In any event, I'd suggest rsync, webfs, python -mhttp.server or otherwise anything else than dd.

199 points by jllyhill 1mo ago

I remember we played warcraft 2 over ~15m of cat3 cable stretched outside between two flats on 6th floor. Those were the times, lol.

bronlund 1mo ago
I remember playing over a 9-pin RS232 null cable - but I guess that is telling about my age :D Not Warcraft though - some ancient DOS game.
- croon 1mo ago
  I believe the first Command & Conquer was the one I played that way. But I'm young, so it can't possibly be the same, can it?
  - doublerabbit 1mo ago
    The original CnC allowed you to play 1v1 via telephone number. Being 15, that was absolute wizardry. It would still works today if both parties have a landline.
    - me-vs-cat 1mo ago
      Landline? I don't understand. If both parties have a LAN line, shouldn't they use that to communicate?
- Hikikomori 1mo ago
  Played Doom over null cable at home.
- inigyou 1mo ago
  Before the world standardized on Ethernet/IP, Microsoft had an abstraction layer called DirectPlay. ("Direct" was that era's "Copilot" word for Microsoft)
  - pezezin 1mo ago
    FYI, EtherNet/IP is an industrial control protocol, not TCP/IP over Ethernet. Yes, that is the real name of the protocol, a more confusing name could not have been chosen... https://en.wikipedia.org/wiki/EtherNet/IP https://en.wikipedia.org/wiki/EtherNet/IP
    - inigyou 1mo ago
      FYI, IP is a phonetic acronym for "I pee", meaning "I urinate" Two letters can have more than one meaning!
      - pezezin 1mo ago
        Yeah, and it can also mean Intellectual Property. But "Ethernet/IP" is not just "two letters", is a trademarked brand.
        inigyou 1mo ago
        I think the holders of the trademark of Ethernet might have something to say about that.
        pezezin 1mo ago
        Ok, you can go to the ODVA and tell them. https://www.odva.org/technology-standards/key-technologies/ethernet-ip/ https://www.odva.org/technology-standards/key-technologies/e...
    - idiotsecant 1mo ago
      I use E/IP all the time and if i had a nickel for every time i had to explain this to people I wouldnt have to use E/IP anymore.
ButlerianJihad 1mo ago
For anyone today who's got copper wire stretched between any buildings, you are in danger and your configuration is quite unwise. For every standalone building that has a ground, that building also has an electrical potential. This potential is not necessarily the same between two neighboring buildings. When you stretch a copper line between them, you are tempting fate, electrically, not to mention the dangers of lightning strikes and the elements attacking that connection. It is generally recognized that fiber optics are not only very efficient and durable, but also impervious to electrical troubles of the type that may plague inter-building connections. Simply grab switches or routers that support at least one fiber-optic connection, and link up!
- lstodd 1mo ago
  Who cared, we were 15 at the time. Besides you worry too much. Entire cities were wired with cat5 hanged off steel cable between 9 to 15 story buildings in early 2000s, before fiber. Nothing burned down.
  - inigyou 1mo ago
    If your cable is shielded it's liable to spark and trip breakers. Happened to me when one building was horribly miswired (someone swapped live and ground somewhere) and fried part of my computer before the breaker tripped. In the worst case there isn't actually any breaker in the path (they are only on live wires and the worry here is ground loops) so your cable just melts. That didn't happen to me. Unshielded cable is theoretically isolated at both ends but who actually knows with some chinesium equipment?
- EvanAnderson 1mo ago
  I did work for a small community college back in the 90s that had expanded their building multiple times since the 70s. The electrical potential between different parts of the building was significant enough to make wired Ethernet unreliable. (I never did understand why this was-- multiple electric service entrances with separate grounds, I assume.) Because of this they were an early adopter of fiber-based networking. I remember being wowed by ATM over fiber running between closets at a blazing 155Mbps (with tons of 10BASE-T clients connected to FORE chassis switches).
sgt 1mo ago
When I did LAN parties we had 10base2 over thin coax. Terminators at each end. Of course it was unstable because people kept disconnecting and everyone lost connection.

riobard 1mo ago

For the time spent finding the ethernet adapter, plugging the cable, configuring IP addresses, and testing with pings, any decent portable SSD drives should have finished copying tens of GB of data.

yjftsjthsd-h 1mo ago
As the article says, > Removable storage is quite slow unless you are willing to spend a lot of money. An SSD good enough to copy tens of GB quickly is not cheap.
- riobard 1mo ago
  At this particular point in time, yes SSD is expensive. But 5~10Gbps USB 3.0 SSD had been very affordable for a long time before 2025.
  - debugnik 1mo ago
    Unluckily for us, and the author at the time of writing, we're in 2026.
    - Dylan16807 1mo ago
      You can still get a drive that will beat the ethernet connection by a lot for $50. But also I'd feel weird if I didn't have at least one good flash drive somewhere, so anyone like me would already have it. I'm going to ignore the part where the USB port described in the article sounds broken. A 100% functioning cable, especially a short one for a drive, is not hard to find.
    - riobard 1mo ago
      If you haven't yet got any portable drives in the drawer, chances are high that you rarely need to copy large amount of files around anyway. In which case free tier of cloud sync services would be preferred for the majority of users.

steve1977 1mo ago

People discovering that network cables can be used to network things. And then calling it a "trick" (I'm surprised it's not a "hack" actually).

alnwlsn 1mo ago
There is always some young person or new to the field learning for the first time. Post like this are exactly how I learned.
concerned_user 1mo ago
Back in the day you needed a modified cable for this with RX/TX swapped on one end but nowadays probably all nic chips have auto-detect so you can take a normal patch cable and do it.
- bronlund 1mo ago
  Yeah, I remember those. When setting up an ad-hoc network, you were like; "where the eff is the crossover cable!" :D
  - luz666 1mo ago
    it was the red one, right?
    - bronlund 1mo ago
      Mine was just a custom made gray one, but I have seen those red ones, yes :D
      - Ekaros 1mo ago
        I bought bunch of ready made 10 meter cables for lan party dunno 15 or 20 years ago... Used with switch... Grey with nice paper label at end with "Cross over"... Haven't had any issues with them ever in regular use... So pointless even back then...

nkurz 1mo ago

It would be nice if this article defined a "ethernet patch cable". I think he's just using "patch" as a slang term for a short cable and it actually works with any length of standard cable, but I'm not certain. Traditionally (pre-2000?), one had to use a special "crossover cable" to do direct connections like this, but apparently modern Gigabit ethernet adapters are able to detect this situation automatically?

bronlund 1mo ago
The way I learned this, is that patch cables use stranded wires, but ethernet cables use solid wires.
- globular-toast 1mo ago
  They are all just twisted pair cables, probably Cat5e or Cat6 etc. The solid ones are usually used for structured cabling, inside walls and trunking, that doesn't often move. Structured cabling is terminated into keystones or patch panels, the "female" end. Patch cables are outside of walls and designed to be moved around and plugged and replugged. They are terminated with 8p8c "male" connectors, commonly called rj45. Stranded cable is used because it's much more flexible.
  - TorKlingberg 1mo ago
    This is the same for mains power cables. Permanent installs are usually solid cores, while the "flexi" cables you plug into a socket are stranded.
    - globular-toast 1mo ago
      Yep, up to a certain point. Thicker wires like 6mm^2 are stranded again, but the strands are very thick and few.
lstodd 1mo ago
IIRC crossovers are pre-2000, yes. "Fast Ethernet" or 100Base-T adapters usually could talk over straight link. edit: as for length, it depends. you won't get a gigabit over 150m of crap cat3, but you will get a link, even if it's 10 half-duplex.

ButlerianJihad 1mo ago

It seems a strange choice, for the demo and for the script, to manually configure addresses on both ends. If your TCP/IP stack is functioning properly, this will not be necessary. Once DHCP fails, you should get a pair of 169.254.0.0/16 (APIPA) addresses, and then Bob's your uncle. Configuring all this manually adds extra complexity when it seems that the goal is simply to connect up your cable and let 'er fly.

rmunn 1mo ago
Back in my college days, 169.254.x.y addresses were the bane of my existence, because my job was getting students' computers set up with the brand-new Ethernet connection in their dorm room. This usually required a tech to come out to their room and configure Windows 95 properly, with IP and DHCP instead of Novell Netware and IPX (I don't remember why Netware/IPX was the default on so many Windows 95 installs, but that was definitely what I found most often when I went to look at someone's computer that "wasn't connecting to the Internet".) Occasionally we had someone who knew what they were doing and had their Windows 95 settings set up correctly, and then all we had to do was activate their room's Ethernet port and add their MAC address to the DHCP server's list of authorized MACs. But most often I or one of the other techs had to head down to the person's dorm room and set up their computer's network settings correctly before it would work. Once the 169.254 address was replaced by 192.168, my job was finally done. But there were times when that took some doing.
- kjs3 1mo ago
  I don't remember why Netware/IPX was the default on so many Windows 95 installs Because Quake multiplayer originally used IPX, not TCP. At least, that's why I had IPX loaded...
ma2kx 1mo ago
And if you prefer ipv6 you can as well just ping -6 ff02::1%eth0 (or eno1 or whatever your devices name in the particular subnet is) and receive all fe80 addresses of other hosts in the subnet. Also, why is he talking about "ethernet"? Its the IP layer, not the ethernet layer...
1mo ago

yjftsjthsd-h 1mo ago

I am 95% confident you don't actually need to assign IPs. Do this: # ping all link-local devices on an interface: ping ff02::1%eth0 And then do your socat/rsync/whatever to the only IP that responds.

steve1977 1mo ago
I would assume so as well, I'm not sure if all host operating systems act the same though. But you could probably just wait a couple of seconds and the interfaces would have assigned themselves link-local addresses.
- QuantumNomad_ 1mo ago
  > I'm not sure if all host operating systems act the same though I have two USB-C Ethernet adapters laying around that I bought some time ago. I connected one of them to a Linux machine and the other to my MacBook Pro and experimented a little bit. All of the following commands and outputs are from the MacBook Pro. The USB-C Ethernet interface is en8. On the macOS side, I can see that a 169.254.xx.xxx/16 IPv4 address has been assigned by macOS as there is no DHCP running on the link, and it has an fe80::xxxx:xxxx:xxxx:xxxx%en8/64 IPv6 address assigned by macOS as well. (The x-es in the aforementioned IPv4 and IPv6 addresses were put there by me in this text. On the system they are decimal and hexadecimal digits in the IPv4 and IPv6 addresses respectively.) The first attempts, relating to ssh, maybe would not work on any system anyway? Not sure how the ff02 multicast prefix for link-local scope works exactly and what its limitations are. % ssh ff02::1%en8 ssh: connect to host ff02::1%en8 port 22: Address family not supported by protocol family % ssh -6 ff02::1%en8 ssh: connect to host ff02::1%en8 port 22: Address family not supported by protocol family % ssh -B en8 -6 ff02::1%en8 ssh: connect to host ff02::1%en8 port 22: Address family not supported by protocol family % ssh -B en8 -6 ff02::1 ssh: connect to host ff02::1 port 22: Address family not supported by protocol family Trying ping: % ping ff02::1%en8 ping: cannot resolve ff02::1%en8: Unknown host I then tried a couple more variations with ping similar to the variations I did with ssh, before moving on to ping6. Seems that the ping command on macOS is IPv4 only. I don't see any -6 flag for the ping command in the man page on macOS. But there is the ping6 command for IPv6, which I have used before (just not with ff02 addresses). Finally, ping6: % ping6 ff02::1%en8 PING6(56=40+8+8 bytes) fe80::xxxx:xxxx:xxxx:xxxx%en8 --> ff02::1%en8 16 bytes from fe80::xxxx:xxxx:xxxx:xxxx%en8, icmp_seq=0 hlim=64 time=10.893 ms 16 bytes from fe80::yyy:yyy:yyyy:yyyy%en8, icmp_seq=0 hlim=64 time=14.365 ms 16 bytes from fe80::xxxx:xxxx:xxxx:xxxx%en8, icmp_seq=1 hlim=64 time=0.511 ms 16 bytes from fe80::yyy:yyy:yyyy:yyyy%en8, icmp_seq=1 hlim=64 time=2.467 ms 16 bytes from fe80::xxxx:xxxx:xxxx:xxxx%en8, icmp_seq=2 hlim=64 time=0.440 ms 16 bytes from fe80::yyy:yyy:yyyy:yyyy%en8, icmp_seq=2 hlim=64 time=2.393 ms ^C --- ff02::1%en8 ping6 statistics --- 3 packets transmitted, 3 packets received, +3 duplicates, 0.0% packet loss round-trip min/avg/max/std-dev = 0.440/5.178/14.365/5.422 ms Worthy of note is that when I ping6 ff02::1%en8, I get responses from both side of the connection (the ones I substituted with fe80::xxxx:xxxx:xxxx:xxxx%en8 are the same IPv6 address that I see for the en8 interface in ifconfig output on my MacBook Pro, and the ones I substituted with fe80::yyy:yyy:yyyy:yyyy%en8 are the IPv6 address of the other end of the link-local connection). Attempting to ssh to the IPv6 address from the ping6 output, making sure to pick the one that is not the IPv6 address of the ethernet interface that is connected on the MacBook Pro side itself: ssh fe80::yyy:yyy:yyyy:yyyy%en8 Output of that I will omit for brevity, but it is the standard question about accepting the ssh fingerprint of the machine and letting me know that this fingerprint is previously known by another name, as I have previously ssh'd into that machine from this one but using the .local mDNS hostname rather than this fe80 IPv6 address. So it seems that having ping6 ff02::1%en8 up the sleeve is useful indeed on macOS too, as long as one knows to use ping6 and not just ping, and that attempting to ssh to ff02::1%en8 does not work directly from macOS at least not for me.

yitchelle 1mo ago

This remind myself the good old 8bit days of using a cross-over RS232 cable to send a file from one computer to another. even at 30bps, it was much more reliable than write my data to a cassette tape on one computer and then reading on the other.

ErroneousBosh 1mo ago
I have plugged two ZX Spectrums together and done LOAD "" on one and SAVE "THING" on the other to transfer data. If you get away from BASIC commands and copy the tape routines up into RAM you can mess with the timing values, and with care you can get it from an average of 1800bps up to around IIRC 12000bps before things really fall apart. Probably with better interfacing you'd get even faster. With more conservative values, this is how "speedloaders" worked. In the late 80s or early 90s one publisher released games on CD where it would load in the loader at normal rate then ramp up to some unholy speed that CD had the bandwidth and stability for but tape did not.
hdgvhicv 1mo ago
232 crossover was still going in the PC era with laplink. Parallel was an option too if I remember. Used to play Duke Nukem 3D over a null modem serial cable. In the days of the spectrum where you loaded via an analog audio input from a tape, and saved via the output, you could move from one to another in the same way, skipping the tape. Apparently this was about 1kbit per second.
inigyou 1mo ago
But did you ever plug one computer's cassette out directly to another computer's cassette in?
- yitchelle 1mo ago
  Not possible on my system. It was only computer<->cassette connection.
  - inigyou 1mo ago

rmunn 1mo ago

That used to require a crossover cable; I've done precisely that (with a crossover cable) back before https://en.wikipedia.org/wiki/Medium-dependent_interface#Automatic_MDI-X https://en.wikipedia.org/wiki/Medium-dependent_interface#Aut... became widespread. With a straight-through cable, you'd be connecting the Transmit (TX) pin of one adapter to the TX pin of the other one, and the Receive (RX) pin of one to the RX pin of the other — and neither device would "hear" the messages the other one was sending. A crossover cable flipped those wires, so each device's TX pin was connected to the RX pin on the other end, and both devices could "hear" each other. But with auto MDI-X, each device would notice "hey, I'm sending but not receiving anything," and would try flipping its Transmit and Receive functions around (transmitting on the RX pin and receiving on the TX pin). Since each device waited a random period before doing that, it was very unlikely (nigh-impossible) that they would both flip at the exact same moment. And if they did, the second interval would most likely not be identical either. I'm simplifying a bit in the explanation above, but that's the broad strokes. And that's how my carefully-labeled crossover cables started gathering dust. (And then I realized "hey wait, I can just use these as normal cables now", and pulled them back out of storage and mixed them with my normal patch cables).

soundworlds 1mo ago
That wasn't that long ago was it..? /looks longingly out the window, and catch my aging face in the reflection
- abrookewood 1mo ago
  Yup ... still have some old 'xover' cables lying around - all of which are RED in colour to explicitly declare their usage
  - valleyer 1mo ago
    Interesting. I don't remember my crossover cables being marked that way; you had to read the dot-matrix printing along the side to know. Color would have been way more handy.

3r7j6qzi9jvnve 1mo ago

tbstream looks fun, but hard to use for the casual user -- not sure if it'll get simpler but I don't think I'll remember messing in configfs just to transfer a file: https://git.kernel.org/pub/scm/linux/kernel/git/westeri/thunderbolt.git/commit/?id=6db21d817b43f8ce5654ccc7aff80d40e4dba4ac https://git.kernel.org/pub/scm/linux/kernel/git/westeri/thun...

ltbarcly3 1mo ago

Ok is there a version for usb-c? Because that would be 10x or more faster and I have a usb-c port and a usb-c cable at all times.

Ballas 1mo ago
If one of the devices support DRD (OTG), but unless one of them is an ARM device, chances are slim.
- xuhu 1mo ago
  Could a smartphone sit between 2 regular laptops to achieve this with 3 USB cables and a hub ?
  - rcxdude 1mo ago
    You would need a USB hub that could turn a USB device into two USB device ports, which I don't think exists. (hubs are essentially only a host-side thing).
- rcxdude 1mo ago
  With USB-C this is a lot more likely, the main issue is going to be software support (Decent chance you could hack something up if one of the devices is running linux. No idea if anything exists for windows).
kotaKat 1mo ago
https://www.amazon.com/Hagibis-Ethernet-Portable-Thunderbolt-Compatible/dp/B0FC1HSS9X https://www.amazon.com/Hagibis-Ethernet-Portable-Thunderbolt... Carry a couple USB-C to RJ-45 dongles ;)
- johnwalkr 1mo ago
  What a clever idea. I carry an ethernet dongle but this one is just the male end and a female usb-c port, meaning your existing usb-c cable is useful and you don't need to carry an ethernet cable.

superdisk 1mo ago

I used to do this to play Minecraft with my cousin without a router.

Yannik_Sc 1mo ago

The USB/Thunderbolt one is a nice catch and good to know if you want to move you data to a new PC. Dell XPS (with soldered SSD) to Framework move just took a few minutes by dd'ing through the created network interfaces (it's different from the tbstream). The limiting factor was the Dell's SSD actually.

johnwalkr 1mo ago
I've been doing this for years between MacBooks with a thunderbolt 4 cable. It's very fast and unlike 10Gbps ethernet, doesn't require a bulky, power-hungry[1] adapter. MacOS also will use thunderbolt automatically for Migration Assistant if available. [1]Most people don't realise how much power ethernet consumes. Even 100Mbps ethernet consumes about 0.5W per port and it goes up with higher speeds.
- drnick1 1mo ago
  Indeed, 10Gbps cards and adapters run very hot. I placed an 80mm right under the card in a PCI fan mount to keep the expansion card cool. The fan does not need to spin fast, but some directed airflow seems absolutely necessary.

pcblues 1mo ago

Yup. "Computer to computer should not be seen without a device in between (unless playing ROTT with your housemates)" 35 years ago maybe :) I had serial and parallel socket, and routerless networking happening on my home systems :) Use cases? Emergencies and maybe dedicated backup.

SillyUsername 1mo ago

You can also pipe it through zstd on the fly, for data that compresses well you'll often see 1.5 to 3× the raw throughput, so a gigabit link can effectively move 165–330MB/s. Receiver: socat -u TCP6-LISTEN:1234,reuseaddr STDOUT | zstd -d -c | tar -xpf - -C /destination Sender: tar -C /source -cf - directory | zstd -T0 -6 -c | socat -u STDIN 'TCP6:[fd42:dead:beef::2]:1234' -T0 uses all cores. Bump the level above -6 for more compression, drop it for more speed, but if your CPU can't keep up, high levels will actually slow it down. Already compressed data won't see much benefit.

ElectricalUnion 1mo ago
If you're using specifically zstd, on the sender side, instead of tweaking the whole tunnel once, you can use --adapt to dynamically adjust to i/o conditions.
effdee 1mo ago
Btw, tar(1) on MacOS shows the file currently being processed when you hit Ctrl-T (i.e. when it receives SIGINFO). And talking about signals, dd(1) can show the amount of data it has processed as well as the throughput. The signal depends on the implementation(e.g. SIGINFO for MacOS, SIGUSR1 for GNU).

awruko 1mo ago

I literally had to cross over the cable once. It was some sort of demo and the cross over cable was missing. The local computer stores didn’t have one and under the time pressure … I have used the pocket knife and convert the cable. It was before 2000 so the speed was limited to 10/100 Mbit - ifconfig did’t report errors and demo went smooth.

sgt 1mo ago

Even easier on macOS. Something like this should work: ifconfig enX inet6 fd42:dead:beef::1 prefixlen 48 No ned to bring it up as it should already be up. enX should be your USB/thunderbolt ethernet adapter, e.g. en6. Then you can go ahead and transfer with socat to your other machine, even if it's a Linux machine. I tend to use nc but socat will definitely be faster. Why the deadbeef network one might wonder? It's private space so won't conflict with public addresses. That being said though, in 99% cases of big files I'll just airdrop the files!

Steltek 1mo ago
ifconfig still probably works on Linux too but it's discouraged because, frankly, it sucks compared to ipconfig2. Most of macOS' CLI feels old and crusty. Which makes sense when you realize it's a fossilized niche BSD from the early 00's.
- sgt 1mo ago
  ifconfig(8) is meant for low level stuff. What Linux did was replace ifconfig with another low level (e.g. ipconfig2), which makes more sense there I suppose. But don't get the impression that ifconfig is the easiest way in macOS on the CLI, it's networksetup(8).
ButlerianJihad 1mo ago
It seems quite strange to me that hackers have adopted "0xdeadbeef" as some sort of generic hex string to use in production. AFAIK, "0xDEADBEEF" originated as a "magic number" in systems like IBM RS/6000 and Solaris, and it was a red-flag number! It meant something in your system was wrong and you'd better check it out! https://en.wikipedia.org/wiki/Magic_number_(programming)#Debug_value https://en.wikipedia.org/wiki/Magic_number_(programming)#Deb... Surely there are more pleasant, vegan hex strings to use, if you want to indicate an ephemeral IPv6 address?
- picofarad 1mo ago
  CAFEBABE? Sexist, so thats out. FACEB00C? In use. Darn this is hard.

brandolini10x 1mo ago

I wonder how we managed to invent the Internet before this trick. Next week's front page will be "Amazing trick: connect two wheels with a platform and you can ride instead of walk"

theodric 1mo ago

"Plug two computers into each other with a network cable and staticly configure the IP addresses" should not be a novel or notable enough idea to trend on HN! This is boggling.

federiconafria 1mo ago
I thought what made the article special was the use of a "patch" cable but the network cards should be able to negotiate anyway, I was very confused about what was the notable thing.
- theodric 1mo ago
  Auto-MDI/X (auto-crossover) was codified in IEEE 802.3ab-1999, the specifcation for gigE, 27 years ago
  - a96 1mo ago
    And it's even been supported really well for almost as long.

1vuio0pswjnm7 1mo ago

"I think it's underappreciated for non-internet applications and doesn't even need a local network: point to point wiring is perfectly fine." In the 1990s I used crossover cable for years with Apple computers that I bought for music production To keep the disk drives "clean", I never connected these computers to the internet If I needed to transfer files to or from Apple computers I connected them to a laptop with crossover cable I grew up using Apple computers that had no internet connection at home and school so this seemed perfectly natural I used computers running Windows 3.11 that had no internet connection, only LAN Needless to say, "Big Tech" companies like Apple are not what they used to be These companies don't really produce anything to be used "offline" anymore. Watching the default network traffic from "Big Tech" marketed computers and software is sad Not automatically trying to phone home is bad for the "business" of data collection, surveillance and ad services There used to be a different attitude toward the internet; there was less trust. I can still find traces of this in the archives at textfiles.com

slipperybeluga 1mo ago

[dead]

yonatan8070 1mo ago

My usual method for this is to spin up a small webserver using the built-in Python module: python -m http.server Then just wget the file I need from the other system.

bitpush 1mo ago
But that requires both the machines to be on a network right? I believe what OP is demonstrating two (isolated) machines talking to each other.
- yonatan8070 1mo ago
  It works just as well if they're on a direct link as demonstrated in the OP, as long as there's working IP connectivity. This isn't to say the way it's done in the OP is wrong, socat is also great, and you can also compress them on the fly by piping through zstd as others mentioned in this thread.
  - bitpush 1mo ago
    Apologies if this is obvious but I'm not following it. > as long as there's working IP connectivity. Dont you need to be on a network to get 'IPs'. It is usually a router's job to setup the network, and also provision IPs. Two devices, not connected to a LAN has nothing. No IP, except 127.0.0.1 and localhost. So then, how do you talk to another device. There isnt an address. OP's article is essentially setting up a P2P connection when there's no third party (router)
    - zamadatix 1mo ago
      Two devices connected to each other are just another form of LAN - one with 2 nodes instead of many. You can manually configure IPs without a router exactly as this article demonstrates: # On sender... ip address add dev eth0 fd42:dead:beef::1/48 ip link set dev eth0 up # On receiver... ip address add dev eth0 fd42:dead:beef::2/48 ip link set dev eth0 up The first 2 lines are run on one host and the second two lines on the second host. The 1st line of each segment sets the IPv6 address to use and the second line of each segment makes the adapter enabled. Plug an ethernet cable in and they can reach each other. As to why, just think of it as "the same way the computer would figure out how to send a packet to the gateway, just to another client in the network segment instead" You only need a router set up to go to a different subnet. If both hosts are in the same subnet then it's just a neighbor resolution (well, you can do neighbor discovery manually too if you really want... but, since it's automatic, no reason too) followed by ethernet bridging. Two hosts with nothing else just plugged into each other should actually already have assigned themselves IPs you could use for this though. They are known as IPv6's link local addresses and are explicitly meant for communication on the local subnet. Ethernet & IP are fun abstractions to really get into the weeds about. When it comes to running networks it's actually a bit of a fight to try to make sure only the addresses the router allows can be used! A whole bevy of technologies address that for the different protocols.

throwaway67743 1mo ago

But... link local precludes the need to configure addressing, even without v6, broadcast ethernet frames exist... why do people keep posting dumb solutions to already solved problems?

doublerabbit 1mo ago

Next up, token ring networks. Remove one cable and the network falls flat, or I thinking of another topology? I do wonder sometimes how the world would be operating if IPX was the primary ethernet. I never got to play with it.

constantlm 1mo ago

If this doesn't work, you could always try Laplink with a parallel cable

icar 1mo ago

I remember doing this at uni, networking labs

snvzz 1mo ago

>over an Ethernet patch cable Was I alone in expecting it to be used in an unconventional way? Like, MAC level with not a trace of TCP/IP, or not even Ethernet but, say, uart over the wire. In any event, I'd suggest rsync, webfs, python -mhttp.server or otherwise anything else than dd.