Develop Reference

How to access single USB devices of a Composite USB device?

I would like to send data from my Windows computer to my Android Mobile.
For this, I need to activate the Accessory mode of the Android device and the USB Host mode on the Windows device.
On my Windows computer, I have a USB Composite device for the Android Mobile. This Composite USB device bundles several interfaces: Enumeration of USB Composite Devices.
Unfortunately, I can't find information how I can access the single devices of a Composite device.
I want to get a device id / path, which I can open with CreateFile to use the created HANDLE for opening a WinUsb handle with WinUsb_Initialize.
But if I try to open a Composite USB device with CreateFile, I get a ERROR_NOT_ENOUGH_MEMORY result.
I'm using this code:
_deviceHandle = CreateFile(
deviceId, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_NONE, NULL,
OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
... with the filename "\?\USB#VID_04E8&PID_6864#RF8NB0NMT0X#{a5dcbf10-6530-11d2-901f-00c04fb951ed}"
It's a GUID_DEVINTERFACE_USB_DEVICE device id for a Samsung Galaxy mobile with enabled USB debugging.
As the driver Windows uses ssudbus2.sys, Version 2.17.16.0 (2021-09-14) from Samsung Electronics Co. Ltd.
The app MyPhoneExplorer can access to my mobile. So it a solution without a special driver must be possible.
How can I get this device id / path of the single USB devices inside a Composite USB device?

The filename you are using represents the overall USB device; it doesn't represent any particular instance. A filename that represents interface will have something like &mi_01 right after the product name, where 1 is the 0-based interface number.
You might be able to just insert the appropriate &mi_xx string into your filename at the appropriate place and get it work. I think you'd also need to modify the GUID at the end of the string, which is the device interface GUID.
The more standard way to find the filename in code is to use the SetupAPI and the configuration manager (CM) API to iterate through all the child devices of your USB device. Look for a child whose device instance ID (retrieved with CM_Get_Device_ID) contains MI_xx where xx is the two-digit interface number you are looking for.
It takes a lot of effort to write up this code in standalone form, and test it, and debug it, so I will not be presenting you with a working code example. Instead, I encourage you to look at the working code in the get_interface_composite function of libusbp which does what you need to do:
https://github.com/pololu/libusbp/blob/759f48d/src/windows/interface_windows.c#L86
There are some more steps to get the path of that device node. And then the code that actually calls CreateFile and WinUsb_Initialize is here:
https://github.com/pololu/libusbp/blob/759f48d/src/windows/generic_handle_windows.c#L56-L77

Android 7 reserved IP ports restriction

In Android 7, there is a range of reserved IP ports.
This is indicated in the file /proc/sys/net/ipv4/ip_local_reserved_ports:
32100-32600
My application uses a port in that range and I get an error "bind : address already used".
So, I wanted to know if there is a way around this restriction?
I thought to modify the file and exclude the port that I use. In fact I have rooted my device, modified the file but changes were not picked up by the kernel.
Even if the file has been modified, if I restart the device the changes are lost.
Is there a way to circumvent this restriction?
Or somehow force the kernel to take into account my changes?

From https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt:
ip_local_reserved_ports - list of comma separated ranges
Specify the ports which are reserved for known third-party
applications. These ports will not be used by automatic port
assignments (e.g. when calling connect() or bind() with port
number 0). Explicit port allocation behavior is unchanged.
The format used for both input and output is a comma separated
list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
10). Writing to the file will clear all previously reserved
ports and update the current list with the one given in the
input.
Note that ip_local_port_range and ip_local_reserved_ports
settings are independent and both are considered by the kernel
when determining which ports are available for automatic port
assignments.
You can reserve ports which are not in the current
ip_local_port_range, e.g.:
$ cat /proc/sys/net/ipv4/ip_local_port_range
32000 60999
$ cat /proc/sys/net/ipv4/ip_local_reserved_ports
8080,9148
although this is redundant. However such a setting is useful
if later the port range is changed to a value that will
include the reserved ports.
Default: Empty
So, I wanted to know if there is a way around this restriction?
I suggest you to use a different port, or else your system may become unstable for a system service may be using a port in that reserved range.
Is there a way to circumvent this restriction? Or somehow force the kernel to take into account my changes?
Since you rooted your device you can try sysctl. These links may help: Android Edit Sysctl Settings and https://forum.xda-developers.com/showthread.php?t=1470125.

How can I read files from usb device on android?

I'm trying to create something like file explorer through connected usb devices(via OTG or usb ports on android TV).
All I need for this is a path something like "/storage/sda4" and device identifier, and then I can work with device through simle android class File. Is sounds simple but I can't find any info about this, but all file explorers can do it (for example ESExplorer).
Ok, I find a simple way to get all connected usb devices with identifier
UsbManager usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
usbManager.getDeviceList();
but how can I get an info about path? deviceName contains something like this "/dev/bus/usb/00x" but it can't help me, I need simple emulated android path ("/storage/sda4"). This page https://developer.android.com/guide/topics/connectivity/usb/host.html tells that I need to get UsbInterfaces and make UsbConnection to bulk transfer and other bullshit, I done it all but didn't find path to device or any other info about usb file list.
Ok, I find another way to get (that don't requires permission!) to get path to all connected devices
StorageManager storageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
Method getVolumeListMethod = StorageManager.class.getDeclaredMethod("getVolumeList");
Object[] storageVolumeList = (Object[]) getVolumeListMethod.invoke(storageManager);
and it works but I need to identify a device(because I want to cache files of different usb storages) but all that I can get from volume object is mStorageId, mDescriptionId, mPrimary, mRemovable, mEmulated, mMtpReserveSpace, mAllowMassStorage, mMaxFileSize, mOwner, mUuid, mUserLabel, mState, mSubSystem.
None of this can not identify the device: mDescriptionId and mStorageId are
unique fot usb port, mUuid is null, mUserLabel is not unique.
Environment.getExternalFilesDirs() won't help, it don't provide any device id and works only with one device.
I find a similar question here, but it has no right answer Android list files from USB Drive.
Well, is a simple way to get list of usb devices with path and identifier exists?

All I need for this is a path something like "/storage/sda4" and device identifier, and then I can work with device through simle android class File
No, because you do not have arbitrary access to removable storage, including USB OTG drives, on Android 4.4+.
all file explorers can do it (for example ESExplorer)
Pre-installed "file explorer" apps may have additional rights granted to them by the device manufacturer or custom ROM developer. Otherwise, they too do not have arbitrary access to removable storage.
is a simple way to get list of usb devices with path and identifier exists?
Not with a filesystem path, no. getStorageVolumes() on StorageManager will give you a list of storage volumes, which includes external storage and removable storage. You can then use createAccessIntent() on StorageVolume to ask the user for permission to work with the volume. If they grant permission, you get a Uri back that:
Serves as a temporary identifier for the volume (i.e., will no longer be usable as an identifier if the user ejects the media, but until then, can distinguish one volume from another), and
Lets you work with a portion of the contents of that volume, though using Uri values, not filesystem paths

UID of a NFC/SWP-accessed SIM card

SIM card is used as a secure element in my project. It is accessed through NFC-SWP contactless interface from a terminal device.
I need to identify the SIM card somehow with a unique and permanent identifier and I need to be able to read the identifier through NFC. ICCID seems to be the best choice, but I would have to expose the EF ICCID file through the contactless interface, which might be dangerous. Moreover, the EF ICCID file is out of my scope on SIM card - access to my dedicated security domain is all I have.
I also tried to use the 4-byte long UID specified in ISO/IEC 14443 Type A, but I get a different UID each time I read the SIM card through NFC. Why?
Another solution would be accessing the card serial number through Global Platform Get Data command (Card Production Life Cycle Data (CPLC)), but I would have to be able to select the card manager through contactless interface, which is forbidden by default and not recommended because of security.
Is there any typical way to solve this issue?

The 4 byte UID for type A (same for PUPI for type B) is allowed to be random (ISO 14443-3, chap. 6.4.4 "fixed unique number or random number"). Their purpose is only, to select one of several cards currently in the field of the reader. Therefore the description of UID is in the anticollision chapter.
Getting the serial number of the card is surely the solution, but since this allows card tracking (I do not know, who this is, but she was present 10 minutes ago already) in privacy-aware context it is frequently only allowed after some kind of authentication (and possibly establishing a secure channel, so eavesdroppers don't benefit). For ideas, how to handle this, take a look at the ICAO specifications under BAC or EAC. I would not expect to find a privacy-aware solution for a card without being able to place specific information onto it.

Getting Manufacturer Vendor ID for ADB

Is there any "universal" vendor ID that I can use so that ADB can detect my China-made Tablet? I can't find the vendor ID of the manufacturer. When I look into Device Manager in Windows the Vendor is a string and not a number. The device is a Cherry Mobile Fusion Bolt tablet.

Try this tool if you are on a windows machine- lsusb Link
If you are on a linux machine, you can run the lsusb command.
The tool is for windows platform. Run it while your tablet is connected through a USB. It may show your Vendor ID. If it does, you can try manually adding it to [USER_DIRECTORY] / .android / adb_usb.ini.

The vendor ID of the device can not be modified without replacing the software on the device (read a new AOSP installation). To use the Google driver, the Vendor ID of the product needs to be known.
Finding Vendor ID in Windows
Start Device Manager
In the Hardware tree, right-click the hardware entry for the device for which the Vendor ID is to be determined.
On the Details tab, set the property drop-down to be "Hardware Ids". The Vendor ID is the 4 character hexadecimal number following the letters VID_. In the case below, the Vendor ID is 18D1:
The PID_, which follows, is the Product ID. It also has a 4-digit hexadecimal number.