hu | Utilities for open source developers

I am working on a p2p application and to make testing simple, I am currently using udp broadcast for the peer discovery in my local network. Each peer binds one udp socket to port 29292 of the ip address of each local network interface (discovered via GetAdaptersInfo) and each socket periodically sends a packet to the broadcast address of its network interface/local address. The sockets are set to allow port reuse (via setsockopt SO_REUSEADDR), which enables me to run multiple peers on the same local machine without any conflicts. In this case there is only a single peer on the entire network though.

This all works perfectly fine (tested with 2 peers on 1 machine and 2 peers on 2 machines) UNTIL a network interface is disconnected. When deactivacting the network adapter of either my wifi or an USB-to-LAN adapter in the windows dialog, or just plugging the usb cable of the adapter, the next call to sendto will fail with return code 10049. It doesn't matter if the other adapter is still connected, or was at the beginning, it will fail. The only thing that doesn't make it fail is deactivating wifi through the fancy win10 dialog through the taskbar, but that isn't really a surprise because that doesn't deactivate or remove the adapter itself.

I initially thought that this makes sense because when the nic is gone, how should the system route the packet. But: The fact that the packet can't reach its target has absolutely nothing to do with the address itsself being invalid (which is what the error means), so I suspect I am missing something here. I was looking for any information I could use to detect this case and distinguish it from simply trying to sendto INADDR_ANY, but I couldn't find anything. I started to log every bit of information which I suspected could have changed, but its all the same on a successfull sendto and the one that crashes (retrieved via getsockopt):

I'm writing a jetpack compose android app, I need to store some settings permanently.

I decided to use androidx.datastore:datastore-preferences:1.0.0 library, I have added this to my classpath.

According to the https://developer.android.com/topic/libraries/architecture/datastore descripton I have added this line of code to my kotline file at the top level:

val Context.prefsDataStore: DataStore by preferencesDataStore(name = "settings")

But I get a compile error:

I have an array of object and I want to make a filter when a language does not exist use an another one. For example when I'm searching for the langauge de and it is not exist I want to search in this case to language en

We are trying to find if the char in A$symbol matches any of the char in B$symbol. Result should be 3 df+ one with matches, one with only in A, one with only in B.

Data example:

I am trying to create a map where I show the amount and category of Exports in every European country, using a scatterpie plot. This is the data I am trying to represent:

I have this Jscharting script which loads data from a csv file. It works great, but unfortunately it doesn't load at all if there is any empty data in the source. How would you add handling empty data into following script?

I was working on currency switcher. i call method on click the link and after method successful want it to reload. but reload is not working at all. currency getting stored in cookie, if i refresh page manually it gets updated in navbar too, but i want it to reload automatically once method complete.

here is the code in navbar..

I PDF signing problems with the latest iTextSharp 5. I know that version is already deprecated, but I must use the older one, because I need to use it in an environment, where no newer than .NET Framework v3.5 is allowed.

For singing documents, the clients may use software or hardware keys. We already used RSA signatures in our company, but now we have toimplement support for ECDsa keys too. That's why I tried to sign PDF files with iText's PrivateKeySignature class, and calling MakeSignature.SignDetached method.

When I use RSA key for signing a PDF, and try to verify signature with European Commission's DSS Demonstration App (https://ec.europa.eu/cefdigital/DSS/webapp-demo/validation), it has no issue with the signature, only that it not accepts the certificate issuer as a trusted CA. That's fine, because I use a test key generated by an internal CA for developer use only.

But if I use ECDSA key for signing a PDF, the DSS Demonstration App says "Signature is not intact.".

The code I use for signing:

I want the following idea: I have short a = -4; and I have an unsigned short b = (unsigned short)a; When I printf("%hu", b), why doesn't it print 4? How can I convert a negative integer to a positive integer using casting?