I am developing embedded microcontroller hardware using a Texas Instruments Starter Kit. I am writing the firmware for the Ethernet link between my microcontroller and x86 Windows desktop.
I have written my own Ethernet driver for the microcontroller and my own protocol driver. So I have absolute FULL control over what data is being transmitted to and from the microcontroller. Up until now, I have managed to write ARP, IP, and ICMP drivers.
I use Wireshark on Windows closely to monitor all data frames going in and out. Now when Wireshark is capturing, "ping" from the console works correctly, but when I stop capturing on Wireshark, my ping fails with "Destination host unreachable." I check the logs on my microcontroller; I see Windows is sending ARP requests, and the microcontroller is replying to them correctly. But the network driver in Windows is filtering them away. So no ICMP requests are being sent. When I check the MAC table using "arp" from the console, my microcontroller is in the list while capturing but not when not capturing its not in the list.
What could be the problem, and how can I debug this problem? Are there any tools/apps for Windows that give statistics on dropped/filtered packets?
I found the problem, there was a punny padding missing in my ICMP echo reply. I did a side by side comparision between a working ping with my wifi router vs my microcontroller on wireshark and found this difference. I thought it wasn't such a big deal, apparently not.
Although what has it got to do with wireshark capturing, I have no clue.
Related
I am running some data throughput tests by sending UDP packets using iperf through a VM that does some sort of processing on those packets.
My application runs in promiscuous mode, so it will pick up all packets.
I saw my application drop some packets, but my application counters show that it was not due to any slowdown or failures.
I put some logs in my application and they suggested that the ethernet frame itself may be corrupted.
I was also running tcpdump on the vnics of both the iperf machine and my packet processor but these packets never showed up in the traces. I was hoping to see corrupted packets appear in the traces.
The commands looked like this:
tcpdump -i vnet11 -C 100 -w iperf.pcap
tcpdump -i vnet7 -C 100 -w sgi.pcap
My doubt is, if the ethernet frame is itself corrupted and the destination MAC itself does not match the MAC address of vnet7 or vnet11, will tcpdump capture those packets?
Edit:
It just struck me that if Ethernet frame itself was corrupted which caused destination MAC to mismatch, then the linuxbridge won't send that packet to my packet processor's vnet interface in the first place. So tcpdump does not have anything to capture here. Please ignore this question.
In fact, if the problem is a corrupt Ethernet frame, you will not see it at all. Your network card will discard the frame and your sniffer will never see it.
Running in promiscuous mode will normally disabled the MAC filtering on your network card so that the sniffer will see all packets, regardless of the destination MAC. However, you cannot see packets that are not sent to the NIC (obviously), so in a switched environment, unless you take additional steps to either attack the switch or configure a span or mirror ports, you will only see broadcasts and frames that are destined for a MAC on your system.
Virtual Machines can complicate this further. Different virtualization solutions handle this in different ways. In some, for instance, the administrator can choose to configure whether or not frames that do not match the host address are delivered to the VM, effectively making promiscuous mode moot.
I have microcontroller pic16f887 and serial ethernet board. When start browser i have problem - the message is this site can't be reached and i can show the content in browser. What may be the problem???? I use HTTPServerExample
http://www.mikroe.com/add-on-boards/communication/serial-ethernet/
Is the IP address configured correct? Wireshark is a very nice tool you can run on your PC to track the TCP/IP traffic and try to detect what goes wrong.
I am developing a logic core to perform data transfer between a FPGA and a PC over ethernet, using a LAN8710 PHY on my FPGA board.
I've achieved to transfer some UDP data packets from the FPGA to the PC. It's a simple core that complies with the PHY transfer requirements. It builds the UDP package and transfer it to the PC.
To check the reception on the PC, I am using Wireshark and as said above, I receive the packets correctly. I've checked the reception with a simple UDP receiver written by myself.
But, I've noticed that I only receive these packets when Wireshark is running on the PC. I mean, if Wireshark is ON, my application receives the packets too, and the counter of received packets of the following picture increases. (This picture is not mine, just one from the internet)
http://i.stack.imgur.com/wsChT.gif
If I close Wireshark, the PC stops receiving packets and the counter of received packets stops. My application stops receiving too.
Although novice on networking topics, I suspect that this issue is related to PC-side. Seems like Wireshark is "opening/closing" the ethernet communication channel, or something like that. Does anyone knows about this issue?
To build a functional core to transfer data between a PC and the FPGA, I've developed a core to transfer and receive UDP packets. Next step will be ARP implementation (to let the PC identify my FPGA board, as I understand). What protocols are necessary to perform full-duplex data transfer between this 2 devices?
Thank you very much in advance,
migue.
Check whether you are able to get appropriate receive interrupt at ethernet driver level on PC-side for a single transmitted packet by FPGA. If you do not get the receive interrupt, check on the transmit side(FPGA) for appropriate transmit interrupts for packet that is being transmitted. This should mostly help you in cornering the issue.
As far as i know, wireshark is just a packet analyzer/sniffer. However, if wireshark is suspected, one option could be to try with alternate packet sniffer to rule out if any such scenario is happening.
A handy tool for determining problems in network and also for determining the network statistics shall be netstat. netstat -sp udp shall list down the statistics only for UDP. There are many other parameters that can be used with netstat for diagnosis.
After many months I solved it, I post to help someone stucked in the same point.
Finally I figured out that Wireshark uses a tool to access the network link layer of the computer. This tool allows Wireshark to sniff all incoming and outgoing packets at a specified network device. To do this, the first step is to OPEN the network device, and that's why my program only worked if Wireshark was open.
Regards.
So I was curious if this is possible at all. Currently i have a program running in a micro controller (digi rabbit) that reads SPI data from a chip. I also have TCP/IP protocol set in this program so it sends the SPI data to the server. Microcontroller is programmed in C. Server is in java. I convert SPI data into string and send it over, the server reads the raw data.
But i wanted to know if there is a way that I can read the data from Ethernet port. So what i want is one end of cat 5 cable on micro controller and the other on Ethernet port of the computer. Just for testing purposes that micro controller port and everything is installed properly, before i turn on the server. I am not that experienced with networking. So if anyone can point to a blog, or any tips that would be great. My question is how would i go about it?
Thank You
What you want to do is called raw Ethernet. Of course this can be done.
On the microcontroller side you need to follow its Ethernet controller datasheet to send out and receive packets. On the PC side this is a bit more complicated and depends on the OS that is running on the PC. On Windows you can use the WinPcap driver to send and receive raw Ethernet packets.
Be aware, that both Ethernet controllers, the one on the PC and the one on the microcontroller, filter all incoming packets that do not contain the receivers MAC address or any multicast/broadcast address. For a simple check the broadcast address (all address bits are 1) will do.
Also note, that the OS on your PC will transmit all kind of packets as soon as the link is established. So you may use a unique protocol identifier in the type field of your raw Ethernet frame. Check Wikipedia's article about Ethernet frames. Btw. don't get confused. You only need to send MAC-adresses, Ethertype and the payload. Everything else, like the CRC, preamble etc., is added by the Ethernet controller automatically.
I have 16 Arduinos that are in very tight spaces and hard to get to when I need to reprogram them with my FTDI cable. I would like to have or create some sort of centralized place where I can connect my FTDI cable, make some sort of selection (switch of some sort), which will then connect the pins my cable is on to the selected arduino.
Does anyone have any thoughts on how this can be accomplished? I've toyed with transistors, but that takes a lot of them and didn't quite work.
Are there any premade solutions that are out there that I have yet to find?
Thanks very much!
Here is a thought! TCP to Serial.
Sound complicated.
Not really.
Note from AVRDUDE's manual the following
For programmers that attach to a serial port using some kind of higher
level protocol (as opposed to bit-bang style programmers), port can be
specified as net:host:port. In this case, instead of trying to open a
local device, a TCP network connection to (TCP) port on host is
established. The remote endpoint is assumed to be a terminal or
console server that connects the network stream to a local serial port
where the actual programmer has been attached to. The port is assumed
to be properly configured, for example using a transparent 8-bit data
connection without parity at 115200 Baud for a STK500.
With this, One could place your Arduino's behind your choice of TCP to Serial Server. Which is available in several forms. Cisco has a gang TS (but that is expensive, unless used). lantronix (and others have single end point devices. But then for Linux, there is "Net2Ser" which can serve up all your ttyS (aka Serial/COM ports).
With the later you could use a raspberry or TP-Link TL-WR703N (
In the latest IDE 1.5.6r2 add one entry for each TCP-to-Serial Port to ./Arduino/hardware/arduino/avr/programmers.txt file. While replacing the IP and Port with corresponding values.
TCP2001.name=TCP 2001
TCP2001.communication=serial
TCP2001.protocol=stk500v1
TCP2001.program.protocol=stk500v1
TCP2001.program.tool=avrdude
TCP2001.program.extra_params=-Pnet:192.168.1.100:2001
TCP2002.name=TCP 2002
TCP2002.communication=serial
TCP2002.protocol=stk500v1
TCP2002.program.protocol=stk500v1
TCP2002.program.tool=avrdude
TCP2002.program.extra_params=-Pnet:192.168.1.100:2002
...
Additionally change "protocol" to "upload.protocol" the following line in ./Arduino/hardware/arduino/avr/platform.txt
tools.avrdude.program.pattern="{cmd.path}" "-C{config.path}" {program.verbose} -p{build.mcu} -c{protocol} {program.extra_params} "-Uflash:w:{build.path}/{build.project_name}.hex:i"
to
tools.avrdude.program.pattern="{cmd.path}" "-C{config.path}" {program.verbose} -p{build.mcu} -c{upload.protocol} {program.extra_params} "-Uflash:w:{build.path}/{build.project_name}.hex:i"
With this you can use "Upload Using Programmer" with the selected programmer to send over TCP, rather then use the Upload.
That all said, it will only work on Linux.
avrdude: ser_open(): network connects are currently notimplemented for Win32 environments