Currently, i'm working with HLK-RM-04 wifi to UART module. I'm using this in server mode. I've connected this module(tx/rx) to my PIC16F887. Connections are fine and I can able to transmit and receive data.
All i'm doing here is giving a html request from a browser/web client, and i'm expecting my data(responded from my MCU) to be displayed in browser. But i'm not getting it properly. Sometimes it works in right way, but most of the time if displays some junk value.
To analyze from MCU side, i tapped my MCUs Tx pin and connected to PC COM port. Yes, it seems it works perfect. I can able to see my data in hyper terminal, what i'm transmitting from MCU.
So to analyze from PC side, I used a free web-sniffer. There I can see data received was junk at sometimes. (Pls refer images) I couldn't able to guess whats wrong ?
Data sent to wifi module from MCU was right, but data sent from wifi module as wifi frames are bad ?
Is that any way to analyze further ?
Expected response - 1 out of 5 request wins:
bad response 2:
I don't remember when I was using HyperTerminal for the last time and I am not sure will it show whitespace characters (if I remember there is such settings).
One of the things that I would try is to install serial port sniffer or some advanced terminal (like Realterm) and verify that there is no some junk in form of white space characters that are hidden in HyperTerminal.
Related
I am receiving data through a TCP socket and although this code has been working for years, I came across a very odd behaviour trying to integrate a new device (that acts as a server) into my system:
Before receiving the HTTP Body response, the recv() kernel function gives me strange characters like '283' or '7b'.
I am actually debuging with gdb and I can see that the variables hold these values right after recv() was called (so it is not just what printf shows me)
I always read byte-after-byte (one at a time) with the recv() function and the returned value is always positive.
This first line of the received HTTP Body cannot be seen in Wireshark (!) and is also not expected to be there. In Wireshark I see what I would expect to receive.
I changed the device that sends me the data and I still receive the exact same values
I performed a clean debug build and also tried a release version of my programm and still get the exact same values, so I assume these are not random values that happened to be in memory.
i am running Linux kernel 3.2.58 without the option to upgrade/update.
I am not sure what other information i should provide and I have no idea what else to try.
Found it. The problem is that I did not take the Transfer-Encoding into consideration, which is chunked. I was lucky because also older versions of Wireshark were showing these bytes in the payload so other people also posted similar problems in the wireshark forum.
Those "strange" bytes show you the payload length that you are supposed to receive. When you are done reading this amount of bytes, you will receive again a number that tells you whether you should continue reading (and, again, how many bytes you will receive). As far as I understood, this is usefull when you have data that change dynamically and you might want to continuously get their current value.
I am a complete CAN bus newbie. I'm hoping someone with CAN experience can point me in the right direction. I was given a Vector VN1610 USB to CAN adapter and a Continental ARS-308 radar sensor. The goal is to read some velocity and distance information from the sensor. Right now I am just trying to see any data but all I get are messages with an id of 0 or 0x80000000. The data payloads all report as 8 bytes of 0.
What Works
I have been able to use the sample .NET code provided and set up the VN1610. The ARS-308 has a single CAN channel so in the Vector Hardware Config for my application I just map "CAN 1" to VN16101 Channel 1. (I leave CAN 2 unassigned) I then assume I use that one channel for both transmit and receive. The code reports that the channel sets up an activates and no errors are reported.
I then have a thread looking for incoming messages. If I don't debug out the two IDs mentioned above I can actually process all of them and then I get XL_ERR_QUEUE_IS_EMPTY messages. So it looks like its all working, I'm just not getting any real data.
What Doesn't
I would think a slew of data messages in the 0x200 - 0x702 range would be coming in for the Continental ARS device. Now I'm more used to ethernet type protocols where I would send a command and then read a response. None of my docs talk about how CAN works so I am ASSUMING that in CAN the device just sends data. I certainly can't find any commands that tell the device to send me the particular msg ID I'm interested in.
Am I missing some basic CAN configuration step that informs the device it should start sending data? Any suggestions at all would be appreciated.
If it matters I'm writing in VS2013, .NET on a Win 7 64 Ultimate machine.
The answer is No. It turns out that CAN devices will indeed just start streaming out messages when you turn them on (well at least this one does). The messages with ids of 0x0 and 0x8000000 are bogus. Even with the radar sensor turned off I continued to see those messages.
It turns out I had a hardware problem. The CAN bus requires a 120 Ohm resistor which was installed. The problem was when the shell was put back on the cable the resistor got cracked. Once we repaired this, everything started working as expected.
I got a problem when using NSInputStream.
I have client app which connect to a server then server will start to send message to my client app through TCP repeatedly about 1 message per second. Server is just broadcasting message to client and message is xml format. The server send a message as one packet.
Now the problem is that when I read byte from NSInputStream the data got truncated which mean instead of receive 1 complete message, I got 2 separate data(partial xml) respond from time to time. I am not able to debug because it already happen when I read data byte from NSInputStream.
I use Wireshark to analyse every packet I receive and when it happen data got truncated too, because TCP so partial data retransmit to my client.
I have tried to log every partial data byte, the sum of partial data always around 1600 byte.
I have no idea how did they design and implement server side, but I do know there are many of people connect to that server and continuous get broadcasting message from it.
Does anyone encounter this problem? Can anyone help? Is it possible that data is over the max size and get splited?
This is not a problem per se. It is part of the design of TCP and also of NSInputStream. You may receive partial messages. It's your job to deal with that fact, wait until you receive a full message, and then process the completed message.
1600 bytes is a little strange. I would expect 1500 bytes, since that's the largest legal Ethernet packet (or especially somewhere around 1472, which is a really common MTU, minus some for the headers). Or I might expect a multiple of 1k or 4k due to buffering in NSInputStream. But none of that matters. You have to deal with the fact that you will not get messages necessarily at their boundaries.
I am using the following few lines of code to write and read from an external Modem/Router (aka device) via IP.
TCPClient.IOHandler.Write(MsgStr);
TCPClient.IOHandler.InputBuffer.Clear;
TCPClient.IOHandler.ReadBytes(Buffer, 10, True);
MsgStr is a string type which contains the text that I am sending to my device.
Buffer is declared as TIdBytes.
I can confirm that IOHandler.InputBufferIsEmpty returns True immediately prior to calling ReadBytes.
I'm expecting the first 10 bytes received to be very specific hence from my point of view I am only interested in the first 10 bytes received after I've sent my string.
The trouble I am having is, when talking to certain devices, the first byte returned the first time I've sent a string after establishing a connection puts a rogue (random) byte in my Buffer output. The subsequent bytes following are correct.
eg 10 bytes I'm expecting might be: #6A1EF1090#3 but what I get is .#6A1EF1090. in this example I have a full stop where there shouldn't be one.
If I try to send again, it works fine. (ie the 2nd Write sent after a connection has been established). What's weird (to me) is using a Socket Sniffer doesn't show the random byte being returned. If I create my own "server" to receive the response and send something back it works fine 100% of the time. Other software - ie, not my software - communicates fine with the device (but of course I have no idea how they're parsing the data).
Is there anything that I'm doing incorrectly above that would cause this - bearing in mind it only occurs the first time I'm using Write after establishing a connection?
Thanks
EDIT
I'm using Delphi 7 and Indy 10.5.8
UPDATE
Ok. After much testing and looking, I am no closer to finding this solution. I am getting two main scenarios. 1 - First byte missing and 2 - "introduced" byte at the start of received packet. Using TIdLogEvent and TIdLogDebug both either show the missing byte or the initial introduced byte as appropriate. So my ReadBytes statement above is showing consistently what Indy believes is there (in my opinion).
Also, to test it further, I downloaded and installed ICS components. Unfortunately (or fortunately depending on how you look at it) this didn't show the same issues as Indy. This didn't show the first byte missing nor did it show an introduced byte at the beginning. However, I have only done superficial testing, but Indy produces the behaviour "pretty much straight away" whereas ICS hasn't produced it at all yet.
If anyone is interested I can supply a small demo app illustrating the issue and IP I connect to - it's a public IP so anyone can access it. Otherwise for now, I'll just have to work around it. I'm reluctant to switch to ICS as ICS may work fine in this instance and given the use of this socket stuff is pretty much the whole crux of the program, it would be nasty to have to entirely replace Indy with ICS.
The last parameter (True)
TCPClient.IOHandler.ReadBytes(Buffer, 10, True);
causes the read to append instead of replace the buffer content.
This requires that size and content of the buffer are set up correctly first.
If the parameter is False, the buffer content will be replaced for the given number of bytes.
ReadBytes() does not inject rogue bytes into the buffer, so there are only two possibilities I can think of right now given the limited information you have provided:
The device really is sending an extra byte upon initial connection, like mj2008 suggested. If a packet sniffer is not detecting it, try attaching one of Indy's own TIdLog... components to your TIdTCPClient, such as TIdLogFile or TIdLogEvent, to verify what TIdTCPClient is actually receiving from the socket.
you have another thread reading from the same connection at the same time, corrupting the InputBuffer. Even a call to TIdTCPClient.Connected() will perform a read. Don't perform reads in multiple threads at the same time, if you are using the threads.
I am getting pretty frustrated, i have an tcp server running on my mac where i have a couple of devices hooked up to. I wanted to have my iphone connected to it so i can run som commands from my iphone directly to my mac # home.
The tcp client for my iphone works pretty good except for one fault, it seems like it doesnt clear up the outputstream for each string i send. Here is an example of what i am having problems with
I type in "Start my browser" on my iphone client and hit send
The message pops up on my mac, everything ok so far
I want to send another command from my iphone and type "B" and hit send
The output on the iphone will then be "Btart my browser"
It seems as it keeps the previous string in cache or something.
Does anyone have any sugestions? I would appreciate all help, if you need to see any of my code please post an message saying so and i will have it posted.
Without any code I can only guess, but this looks like a bug in your code that handles the string input. In case you are using a NSMutableString / NSMutableData to store your input, make sure you clear that input after accepting a command. It now looks like you just overwrite the beginning without actually erasing it first.
The source of the problem was that my server software not emptying the datastream. When I emptied the stream on the server side, it worked perfectly.