I am using an embedded linux kernel 2.6 onto an Intel Atom CPU. Due to the slow performance of the 2x00usb wifi driver, I decide replace it by the 5370sta. Now speed connection is up to 10 times faster but I am experimented a problem with UDP transmission that worked like a charm with the 2800usb wireless driver.
The UDP connection can receive all datagrams properly, but the transmission turn down after some minutes. It is curious because while transmitter is down, the receiver keeps receiving correctly. After some minutes, the UDP transmitter comes alive again. I have not been able to find a pattern, the failure is apparently random, but I am sure that there is a reason, maybe a buffer saturation or something like that.
I have modified the socket bind from (ip=0.0.0.0 to my CPU ip) and the broadcast (from 255.255.255.255 to 192.168.0.255) among several non successful attempts. But I thing that problem is with the new wifi driver and some configuration that I don't know.
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I'm having no joy in getting a replayed UDP Multicast packet to be "seen" by a client program on a different machine.
Details:
I have two machines on my local (wired) network connected through one unmanaged switch. One machine (running tcpreplay) is running Ubuntu 20.04, the other machine is running Windows 10.
On the Windows machine I have a Python program I wrote which listens for UDP multicast packets on port 5110 (this is dictated by the source of the UDP stream which is a commercial program). When I run the commercial program, my Python code correctly consumes the incoming packets and all seems to be working fine. I have a lot of work yet to do on the contents of those packets after they are received, but that isn't important for this issue.
So, moving forward, I decided it would be great to be able to work on the Python code without having the commercial program always running in the background hogging up resources. I figured if I could catch a snippet of UDP broadcasts from that program, I should be able to replay at leisure without having to run that resource hog.
So, on the Windows machine, I captured a UDP multicast packet stream using Wireshark and saved to a pcap file which I then copied to the Ubuntu machine.
I then attempted to replay that pcap file (on the Ubuntu machine) as follows:
$sudo tcpreplay -i enp5s0 single.pcap
To my disappointment, my Python program (on the Windows machine) did not receive the incoming packets.
Back on the Windows machine, I fired up Wireshark again and captured the "replayed" packet coming from the Ubuntu machine - so it appears the packet did make it out of my Ubuntu machine and into my Windows one. The contents of both the source packet (sent by tcpreplay) and the received packet (grabbed by Wireshark) appear identical - including the source and destination MAC addresses and the checksums. A diff on the byte contents of each packet yields no differences.
However, my Python program still stoically sits there waiting at:
data, address = sock.recvfrom(1024)
Here on stackoverflow, I did find this thread which seems to be an identical problem, however none of the solutions presented within helped (including changing the rp_filter parameter). I also saw mention of a Windows program, "Colasoft PacketPlayer", which I tried - running on the same machine as my Python client. This appears to have the same apparent results (i.e. no joy). I did not initially try that route as I was concerned with generating the packet on the same machine which is listening for it. (As an aside, I did also capture the replayed packet from Colasoft PacketPlayer and it too appears identical to the source packet).
At this point I'm out of ideas and am reaching out to the community for possible next steps?
I am monitoring USB traffic with Wireshark in the interface XHC2. However, the payload of all USB packets is all-zero. The packet's length is correct, but the packet's payload is all zero. It does not matter which device, which packet or whichever. It is always zero. Obviously, this is not the reality, since the devices work properly and lot of information is displayed via lsusb.
My guess is that the XHC interface is setting the payload to 0 before delivering to upper layers, but I do not know if it is intentionally, a bug, kernel issue, my fault or something related with Wireshark.
I also tried tcpdump -i XHC2 and the saved pcap file is the same.
Additional info:
Mac Mini M1 with Big Sur
Wireshark ARM 3.6
SIP disabled
It's unlikely to be related to Wireshark, given that it happened when you captured with tcpdump as well.
You should file an issue on Apple's Feedback Assistant.
I have a device connected to a USB and it periodically sends data to my PC. During the time it is not sending data, the USB cable needs to be removed, else, the device won't work (a fail-safe feature, if the USB cable is connected and attached to pc, the device is in communication mode, if the USB cable is disconnected from pc, it is in stand-alone operation mode).
I was thinking to use the Devcon so I font has to use another hardware, I'll just disable the USB port during an operation mode, then enable it during communication mode. However, the periodic transfer of data can be set to every 5,10,15,30 minutes depending on the settings.
My question is, will it be okay to disable/enable the USB port periodically? Say every 5 minutes? Won't it cause any problem in the long run? Or would it be more efficient for me to use external hardware, a switch to connect/disconnect the USB? Appreciate any advice or thoughts.
If devcon works for you, I don't see why it would cause any problems in the long run. There is no inherent reason why the hardware should get damaged when you run some commands in your software to disable a USB port.
Using external hardware to accomplish the same thing would not be more efficient because you'd have to pay for the hardware and maintain it.
After having been studying a USB Packet Sniffer based around the BeagleBoard xM (https://gitorious.org/beagleboard-usbsniffer/), I have been at a loss as to how the driver actually works in a certain area.
I now understand that the BeagleBoard acts as a one port USB hub for the USB host to see, so that it may view and log the packets going through it. The part i'm trying to currently understand is how exactly the BeagleBoard is able to be somewhat transparent, and able to mimic the USB Vendor/Product ID's of the device being sniffed.
There is nothing to mimic. If it behaves as a hub, it can see all the traffic going between the computer and the device under test because all the USB packets would go through the hub. Packets are received by the hub and transmitted along to the other device.
I am working on indoor gps tracking and for this I need a wifi signal logger which can receive the signals from different smartphone(whose wifi is turned on) an send it to a remote server. I wanted to know, where I can get this kind of hardware, having capability to receive signals from different smartphones and log its signal strength and mac address in a remote server.
Please let me know the details.
Thank you in advance.
Pravin Prasad
In simple terms, Wifi clients(smartphones, notebooks etc.) send periodic Probe Request packets to actively seek wifi access points and Wifi APs(routers, gateways etc.) send periodic Beacon packets to advertise the presence of WLAN network.
You can use any wifi capable device like a smartphone or notebook to log the above packets.
Configure your wireless card in monitor mode.
Use a packet sniffer(for example, wireshark) to capture the traffic on the wireless interface or write your own with libpcap. You may filter on the packet type, source, destination etc.