My port scanners don't affect a port that's already open. And a port scanner is usually run at powerup (or manually sometimes) to find out who is where.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Gosh, we never thought about that. That could explain a few things.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Phil Hobbs wrote
Actually it is not. One problem with the Linux kernel and renumbering /dev/ttyUSB* after a re-connect is that the kernel will hang after some reconnects. This can happen if there is a bad contact, quite common, an intermittent contact in the USB connector. From this follows USB serial devices are a no no for any life support system (or anything critical). I have tested this kernel hangup (couple of hundred times does it).
Best is to use ethernet, a TCP or UDP stack is simple to implement and gives you galvanic isolation. Or if you must, use POE.
USB is a Microsoft invention IIRC, looks like a cheap copy of some system I designed a few years earlier.... ;-) About everything that can be wrong with USB is wrong with it.
OTOH for just home use it does work at times.
That said, I have some RTL_SDR sticks plugged in USB, just touch one and the application crashes. BAD connectors. To give you an idea, this PC now has 11 USB ports, just added some more last week after I found the mobo had connectors for more. One free. Booting is... a lot of work... (sequence) good thing it is on 24/7.
Running a terminal program, that would fill up/scroll the screen.
And make scans slow.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thursday, July 19, 2018 at 10:01:03 AM UTC-4, snipped-for-privacy@nospam.org wro te:
-connect
contact in the USB connector.
tem (or anything critical).
ves you galvanic isolation.
I designed a few years earlier.... ;-)
USB was invented by an Intel engineer. The fact that it is in use on every PC made in the last 20 years says to me it must not be too bad. I'd say i t is on a par with the internal combustion engine, lots to complain about, but it seems to get the job done with a minimum of hassle.
the application crashes.
I blame that on the people who think a USB connector barely mounted in a PC is a mechanical support as well as those who use it without an intervening cable so the device can lay on the table. In other words, YOUR fault.
No, bad use of connectors outside of their intended application.
ast week after I found the mobo had connectors for more.
I have no idea why you need so many devices on your PC. There are things c alled hubs to help deal with the mechanical issues.
Rick C.
Yea, they did the processor bug too, and recently... total security disaster. I can only go by what I measure, experience. Too many problems.
You have got a point there, but really is also sucks when used via a cable and a special box. USB cables are just as unreliable, especially the ones that use the thinnest conductors possible. I had a GPS module via USB on a raspberry, luckily the GPIO has a real serial port, no renumbering no problems. See, I have to write all those drivers too, gets complicated really fast, try it.
To get work done.
There are now 8 USB sockets on the back, nice solid place for cables, the rest is on front. I have an USB 1 to 4 hub, jiggling its connector .. well same thing. Back off the PC is more reliable, 4 USB fits in 2 card slots, better connectors than the hub too.
Use ethernet. Do not be a slave of MS crap.
Having the device squirt its ID string out the UART when idle is a
Depends how you do it. First valid command would turn it off. Plus if you like you could make it all non-printing characters.
Nobody says you can't open all the comm ports at once, so if spits out the string every three seconds, you're all connected in three seconds at most.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
In Linux that is not so difficult. Don't know about Windows. However, even opening a not-open port can disturb things. As I wrote I used some ports for "bit banging" and e.g. a relay was controlled by the RTS pin of a port. Opening the port would change the state of the relay.
Linux lets you open a file N times within a single process, which is irritating--you can't use file handles alone to enforce thread safety the way you can in Windows or OS/2.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reading data from a port that is in use disturbs the other user of the port. They won't get that data.
Of course there are plenty explicit locking mechanisms available...
Correction, it's an Intel invention designed to sell the next generations of CPU at the time. By the time USB2 had been established as the standard for about a decade or so, its use as a means of leveraging extra sales of newer more powerful x86 CPUs had pretty well run its course.
It was such a shitty interface, I could well believe in Microsoft having some involvement in its initial launch but it was Intel who were the main beneficiary of its deployment as a "Jack of all trades" interface standard.
-- Johnny B Good
torsdag den 19. juli 2018 kl. 16.01.03 UTC+2 skrev snipped-for-privacy@nospam.org:
but then you need a switch or hub and the guessing game of trying to figure out the IP
Lasse Langwadt Christensen wrote
Yes, switch, but if you design the stuff you can set fixed IP addresses. That is how I do it anyways. If you need names, easier to remember perhaps, specify those in /etc/hosts.
~ # ping router PING router (192.168.178.1) 56(84) bytes of data.
64 bytes from router (192.168.178.1): icmp_req=1 ttl=64 time=2.95 ms 64 bytes from router (192.168.178.1): icmp_req=2 ttl=64 time=0.536 msUsing /etc/hosts may also protect you against DNS spoofing, just today I ran a check after a suspicious browser screen.
Say you did, to find out the IP address of news.aioe.org ~ # host news.aioe.org news.aioe.org has address 46.165.242.91
Now if you enter that in /etc/hosts
46.165.242.91 mynews.aioe.org then anytime you ask for mynews.aioe.org it will get the IP from /etc/hosts, not from the net nameservers, so spoofed DNS is not possible, and it is much faster, and more reliable.~ # telnet mynews.aioe.org 119 Trying 46.165.242.91... Connected to mynews.aioe.org. Escape character is '^]'.
200 news.aioe.org InterNetNews NNRP server INN 2.5.4 ready (posting ok)I deliberately changed news. to mynews. to show the lookup really comes from /etc/hosts. Normally you would enter it as news... All basic networking.
Flexibility, firewalls, MAC filtering, global, local.
torsdag den 19. juli 2018 kl. 21.21.57 UTC+2 skrev snipped-for-privacy@nospam.org:
you'll also need to get the netmask right, I think most people use DHCP which solves that but leaves you with trying to figure out what IP
Am 19.07.2018 um 20:37 schrieb Lasse Langwadt Christensen:
Now, with the avahi demon installed, you can simply write "ping MyScope.local" and it will be found if it is on the lan. Avahi cares about and configures(if needed) only local devices on your own LAN. Just attach a .local to the device name. It is standard on Ubuntu & derived systems like Mint, among others.
You could just as well open the web server page of your DSL router box and see who's there on the lan and what IP address it has been given.
regards, Gerhard
ery
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Compared to what?
nd the
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e and a special box.
est conductors possible.
rial port,
try it.
e last
And I still have no idea.
rest is on front.
ectors than the hub too.
Obviously you need a different USB hub. I've bought units off eBay at bott om dollar prices and found they are so crappy they actually won't work... o r at least very long. It is hard to wade through device to find one that i s good rather than just expensive, but that's not the USB spec or standard, that's the crappy vendors selling us what we will buy.
You mean Intel crap...?
Rick C.
First thing I always do is disable DHCP everywhere. So silly. It may be different with WiFi, but WiFi is, at least these days, totaly insecure, and should be avoided if possible.
I've seen cisco/linkysys switches crash from reconnects (takes about 50 times power-cycling a raspberry pi)
--
?
Have not seen it with my switches, but those are cheap ones, some from ebay... Plenty of raspies here, did you monitor the traffic if it was still asking for the MAC for the IP adress? Sometimes, when for example you switch off the router, it may take up to maybe a few minutes before you get a reply with the MAC of the requested IP address. That effect is 100% reproducable.
If you panic and do a power cycle on the switches it will do a new routing immediately.
I am referring to ARP requests: 07/20-08:43:49.164242 ARP who-has 192.168.178.123 tell 192.168.178.159
I use 'snort' to monitor traffic on the LAN:
snort -i eth0 -v -d
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