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.
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 porting some Windows code to Linux. Part of the windows objects properties was not implemented in .net core's linux implementation. UnicastIPAddressInformation.PrefixOrigin is one of them.
.NET Core code docs show define it as:
value that identifies the source of a unicast IP address prefix.
MSDN defines it as:
Specifies how an IP address network prefix was located.
I am searching .NET Core repo browser for the implementation of this property, which returns the following enumeration:
public enum PrefixOrigin
{
Other = 0,
Manual,
WellKnown,
Dhcp,
RouterAdvertisement,
}
I could not find in .NET Core repo browser a class that implements UnicastIPAddressInformation. In .NET Framework repo browser, I understand the struct IdAdapterUnicastAddress is assigned a PrefixOrigin by marshaling OS data into C# classes/types. Anyway, I do not know at this point how to determine which enumeration value should be applied to a given IP.
Knowing barely nothing about computer networks, I am researching what is an IP prefix and how to figure it out. The practical example I could find was this one. As far as I understand, however, it provides a way to calculate the prefix length. I still need to know how to determine the PrefixOrigin enumeration value to a given IP.
Is it something that can be done by simply taking the prefix length into account ? If not, how do I figure out which PrefixOrigin value a given IP should be assigned ?
This field's value is telling you how a configured (or automatically-configured) IP address on the system was determined.
Manual: Somebody keyed it into the adapter configuration GUI in control panel or set it using e.g. netsh or similar.
Well Known: From a well-known source. I'm not really sure if Windows uses this value. It might be used when a 169.254.x.x address is assigned in the absence of any other configuration and when no DHCP server is present.
DHCP: When a DHCP server automatically assigns an IP address, which is the case in almost all home and office networks (but sometimes not on datacenter networks!), this is how you can tell.
Router Advertisement: IPv6 has an automatic configuration system which was supposed to replace DHCP. To keep things simple, think of this as being functionally the same as the field's DHCP value.
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.
I recently bought a modem that supports CSD (Circuit Switched Data) calls. I put SIM card in it and I am able to make calls via AT commands. But these are always VOICE calls. I have another modem and I need to connect to it via CSD.
I know it is possible because our colleagues are using it this way to access some network.
They are using windows dial-up connection, but I guess that is just something that in the background calls the AT commands.
Nevertheless the dial-up is still giving me "Error 678: Remote computer did not respond". I have tried many settings, but still the same error. I even tried different computer and still got the same error.
So I found out that when I call CSD, then on the receiving side (if AT+CRC=1) it should display +CRING: REL ASYNC. So I setup another modem and called it and it showed +CRING: VOICE.
So how do I convince my modem to call in the REL ASYNC mode?
I already tried:
AT+IPR=115200 or AT+IPR=9600
AT+FCLASS=0 (this is default though)
AT+CSNS=4
AT+CBST=7,0,0 or AT+CBST=71,0,1
AT^SXRAT=0 (this changes the network to GSM)
But still when I do ATDNUMBERIWANTTOCALL; the receiving side shows +CRING: VOICE.
Also my mobile provider ensured me, that the CSD technology is still supported in my country and that I do not need any kind of special SIM card.
You need to remove the semicolon after the phone number in the ATD command: that semicolon is what tells the modem to make a voice call rather than CSD.
Check with your teleoperator does your sim card have separate data number.
Sometimes postpaid (and/or M2M) cards have three different numbers
1. voice
2. fax
3. data
In the end the number could be called normally like it is written in the question, but it only worked in Germany, not abroad...
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.