Background
Been having a lot if issues with this problem. Randomly PC won't connect to NAS for apparently no reason at all, while others it works. I read tonne of posts about various fixes, some worked sometimes, some didn't, but lately none did. Restarting PC, NAS, or router didn't work, nor did changing settings, checking firewall, antivirus, etc.. Finally I managed to figure it out.
Our nas allow us to make a network name to access it by, like \\MyServer, but sometimes when power goes out, or we have to restart router, this address won't work because the server's local IP had changed, and the address was still cached on our computer to the old one.
The reason can be one of many. In my case, it was none that I could find common answers to.
TL;DR
I randomly can't connect to my NAS via \\MyServer or it's IP \\10.0.0.3, but other PC's can.
I suggest using Synology Assistant. This will find the NAS on the network if it is physically in range.
Then I highly recommend to use a fix IP address for the NAS. It is no good idea having servers with DHCP...
Reason (in my specific case)
Sometimes the PC would only connect to the NAS via IPv6 (almost feel like it does it on a whim), IPv4 won't work at all. That or the old IP is cached on your system.
IPv4 looks something like one of these: 10.0.0.5, 172.16.0.2, or 192.168.0.0
IPv6 looks something like: fe80::842a:a43d:3123:1332
Quick fix attempt first
First, just try opening command prompt and enter ipconfig /flushdns, then try to connect to your usual \\MyServer address, see if that works now.
Didn't work?
What you can try is to see if you can connect via its IPv6 — but first you need to somehow obtain it.
Step 1 In command prompt, type ping MyServer (replaced with whatever name you have), and it see if it manages to ping it. If it does, it will resolve the IP and show an IPv6. If it shows IPv4 or can't connect at all, see further down.
Step 2 Locate the IPv6 at the top, remove % and number after.
Step 3 Replace : with -. Note doubles if you have that: :: with --.
Step 4 Prefix the usual \\ at the start, and add .ipv6-literal.net at the end. Now try to connect to the server using that. With the IPv6 example above, it'd be something like: \\fe80--842a-a43d-3123-1332.ipv6-literal.net
Ping shows IPv4?
Try to ping with one of the other computers, or if you are able to, login to the web dashboard or equivalent on one of those computers, and see if you can find any information about the server's IP's, with goal of finding its IPv6.
Once found, do steps above.
Done!
Other stuff:
IPv6 in browser — remove the % and number, put IP inside brackets [] and then connect. Example: http://[fe80::842a:a43d:3123:1332].
Creating alias of the weird IPv6:
Step 1 Right click Notepad, and open as Administrator
Step 2 Go to File → Open, change the dropdown above 'open' from Textfiles (*.txt) to All files (*.*).
Step 3 Locate the hosts file, located at C:\C:\Windows\System32\drivers\etc\ and open
Step 4 At the bottom, write the IPv6 with the colons AND the %##, then a space, then the alias you want it to use (case insensitive). Example: fe80::842a:a43d:3123:1332%15 MyAlias and save. You should now be able to use \\MyAlias to connect to it.
NOTE The %## number is unique to each computer. E.g. your computer gets %15, the next get %7. The rest of the IP is identical. To get the %## number of a different PC, write ipconfig in its command prompt. It should list its own IPv6 with its appended %## at the end.
Another note: If you need to change an IP in the hosts file of an IP that no longer work, you also need to use ipconfig /flushdns again.
Related
Chromebooks at a certain facility will not work with static IPs, and they have reserved IP addresses, but for some odd reason they will not grab those from the DCHP server. By toggling Configure IP address automatically off for a few seconds and back on, the Chromebook gets its reserved IP and works fine. In about 6-8 months we will be changing the entire network and resolving this issue, but in the meantime if I could create a shortcut method for the end users to be able to do this easily it would be a big stone out of my shoe...
I had forgotten I posted this. In order to resolve the issue, I did use "code" and "programming" to create a script that would do what I described above. So, it wasn't a networking question, it was a programming question.
I am a developer of ROS projects. Recently I am trying using ROS(melodic) on WSL2(Windows Subsystem for Linux), and all things works just great. But I got some trouble when I want to use another PC which also in the same local area network(LAN) to communicate with. Before setting the environment variables like "ROS_MASTER_URI, ROS_IP", I know that since WSL 2 work on Hyper-V so the IP show on WSL2 is not the one in the real LAN. I have to do some command like below in order to make everyone in LAN communicate with the specific host:PORT on WSL2.
netsh interface portproxy delete v4tov4 listenport=$port listenaddress=$addr
But here comes a new question:
The nodes which use TCPROS to communicate with each other have a random PORT every time I launch the file.
How can I handle this kind of problem?
Or is there any information on the internet that I can have a look?
Thank you.
The root problem is described in WSL issue #4150. To quote from that thread,
WSL 2 seems to NAT it's virtual network, instead of making it bridged
to the host NIC.
Option 1 - Port forwarding script on login
Note: From #kraego's comment (and the edited question, which I'm just seeing based on the comment), this is probably not a good option for ROS, since the port numbers are randomly assigned. This makes port forwarding something that would have to be dynamically done.
There are a number of workarounds described in that issue, for which you've already figured out the first part (the port forwarding). The primary technique seems to be to create a PowerShell script to detect the IP address and create the port forwarding rules that runs upon Windows login. This particular comment near the top of the thread seems to be the canonical go-to answer, although many people have posted their tweaks or alternatives throughout the very long thread.
One downside - I believe the script that is mentioned there needs to be run at logon since the WSL subsystem seems to only want to run when a user is logged in. I've found that attempting to run a WSL service or instance through Windows OpenSSH results in that instance/service shutting down soon after the SSH session is closed, unless the user is already logged into Windows with a WSL instance opened.
Option 2 - WSL1
I would also propose that, assuming it fits your workflow and if the ROS works on it (it may not, given the device access you need, but not sure), you can simply use WSL1 instead of WSL2 to avoid this. You can try this out by:
Backing up your existing distro (from PowerShell or cmd, use wsl --export <DistroName> <FileName>
Import the backup into a new WSL1 instance with wsl --import <NewDistroName> <InstallLocation> <FileNameOfBackup> --version 1
It's possible to simply change versions in place, but I tend to like to have a backup anyway before doing it, and as long as you are backing up, you may as well leave the original in place.
I ssh into several machines that are just IP Addresses, however I noticed a while back that tab completion stopped working when trying to SSH to them. I use zsh and I can tab complete a regular domain name with ssh, but all the IP machines that I use dont tab complete any more, did something break here? or whats the deal?
OS X - 10.9.3
zsh - 5.0.2
have you set the use-ip style?
zstyle ':completion:*' use-ip true
the documentation says that ip addresses are stripped from the host databases by default. use-ip allows completion of them.
http://zsh.sourceforge.net/Doc/Release/Completion-System.html#index-use_002dip_002c-completion-style
Your ssh might be hashing the entries at known_hosts?
Best usability solution in general for ssh IMO is to create ssh host aliases, and then just use the alias in the command line. Eg. add something like this to you ~/.ssh/config
Host foo
# HostName also accepts numeric IP addresses
HostName XXX.ZZZ.YYY.BBB
then you just use scp backup.tar foo:
Check man ssh_config for more info. From the manual:
HashKnownHosts
Indicates that ssh(1) should hash host names and addresses when they are added to ~/.ssh/known_hosts. These hashed names
may be used normally by ssh(1) and sshd(8), but they do not reveal identifying information should the file's contents be
disclosed. The default is “no”. Note that existing names and addresses in known hosts files will not be converted auto‐
matically, but may be manually hashed using ssh-keygen(1). Use of this option may break facilities such as tab-comple‐
tion that rely on being able to read unhashed host names from ~/.ssh/known_hosts.
Ok ignore the above, I see in a comment that that is not the case, will leave it there for reference though.
PS: you can always manually set the hosts to be completed by zsh using something along the lines of:
hosts=(foo.bar.com faa.bar.com fee.bar.com)
zstyle ':completion:*:hosts' hosts $hosts
Or do a much more complicated version of it, such as described here https://www.maze.io/2008/08/03/remote-tabcompletion-using-openssh-and-zsh/index.html
Does anybody know how to change the COM port number that Windows maps to a USB virtual COM port? You can change this via the Device Manager and clicking on the Advanced button.. but how can you do this via an API, registry change or command line operation?
Any ideas please?
I monitored registry changes during changing COM port 1 to 110 and found modifications in following keys:
[HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM]
"\Device\Serial0"="COM110"
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\COM Name Arbiter]
"ComDB"=hex(3):FC,7F,00,00,00,00,00,00,00,00,00,00,00,20,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\ACPI\PNP0501\1\Device Parameters]
"PortName"="COM110"
You might find this answer useful:
How do I get the friendly name of a COM port in Windows?
It's about finding the friendly name, but I think you'll find it points you towards the right area of the registry, using the 'official' mechanism for locating the right key.
However, if you change the port assignment, you should also update the com port database - see: https://msdn.microsoft.com/en-us/library/ff546481.aspx
When I had to do something similar, I found the right device using the mechanism described in the linked SO article, and then called SerialDisplayAdvancedSettings((HWND)NULL, hDeviceInfo, &devInfoData); to display the advanced dialog and let the OS handle the hard work.
Nowadays you're more and more likely to be encountering odd 'not real' serial ports (e.g. USB ports) which might have other incompatibilities you need to be wary of too.
This changing is done in two below steps in the registry through the "regedit":
Change the name:
In the first step, you need to change the below keys:
In the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\XXX that XXX is your device name. You need to trace each item to find the FriendlyName and then change it as you wish (Ex: "USB Serial Port (6)");
In the previous key, again you need to trace the item to find the PortName and change it to the port number (Ex: "COM6").
Change the port number:
In the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter, you can find the ComDB which is a bit mask of COM ports already allocated. This value should be change based on your COM ports. Note, The first byte controls COM8~1, the second byte controls COM16~9, the third byte controls COM24~COM17 and so on. A value=0 means that the port is not used. A value=1 means that the port is occupied.
Offhand, I don't know how to do it, but here's what I would do:
Use the My Computer/ Device Manager method to assign some unlikely com port, like 61. Then use regedit to search for COM61 and see what Device Manager did.
I know I've seen all these things in the registry somewhere, but a quick search of the knowledge base didn't turn up the answers.
When developing an app that will listen on a TCP/IP port, how should one go about selecting a default port? Assume that this app will be installed on many computers, and that avoiding port conflicts is desired.
Go here and pick a port with the description Unassigned
First step: look at IANA listing :
There you will see at the tail of the list
"The Dynamic and/or Private Ports are those from 49152 through 65535"
so those would be your better bets, but once you pick one you could always google on it to see if there is a popular enough app that has already "claimed" it
If by widely-used, you mean you want to protect against other people using it in the future, you can apply to have it marked as reserved for your app by IANA here
The most comprehensive list of official IANA port numbers and non-official port numbers I know is nmap-services.
You probably want to avoid using any ports from this list (Wikipedia).
I would just pick one, and once the app is used by the masses, the port number will become recognized and included in such lists.
Choosing an unassigned one from the IANA list is usually sufficient, but if you are talking about a commercially-released product, you really should apply to the IANA to get one assigned to you. Note that the process of doing this is simple but slow; the last time I applied for one, it took a year.
As others mention, check IANA.
Then check your local systems /etc/services to see if there are some custom ports already in use.
And please, don't hardcode it. Make sure it's configurable, someway, somehow -- if for no other reason that you want to be able to have multiple developers using their own localized builds at the same time.
If this is for an application that you expect to be used widely, then register a number
here so no-one else uses it.
Otherwise, just pick an unused one randomly.
The problem with using one in the dynamic range is that it may not be available because it may be being used for a dynamic port number.
Well, you can reference some commonly used port numbers here and try not to use anyone else's.
If by "open to the public at large" you mean you're opening ports on your own systems, I'd have a chat with your system administrators about which ports they feel comfortable with doing that with.
Choose a number that is not very common
Choose a default port that doesn't interfere with the most common daemons and servers. Also make sure that the port number isn't listed as an attack vector for some virus -- some companies have strict policies where they block such ports no matter what. Last but not least, make sure the port number is configurable.
Use iana list. Download the csv file from :
https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
and use this shell script for searching for unregistred ports:
for port in {N..M}; do if ! grep -q $port service-names-port-numbers.csv; then echo $port;fi; done;
and put 2 numbers instead of N and M.