TCP Read undifined number of bytes

Hello LabVIEW RT users
I'm trying to convert a java application to my LabVIEW RT Smart Camera
In my camera I have a working TCP server which reads and writes some data to/from a robot. My problem is that in LabVIEW i have to specify who many bytes I'm reciving to get it to work. But in my Java application the BufferedReader took care of this. I can't control what the robot is sending but it could be things like these strings
GET X
SET R 1
SET X 443
SET X 11
GET START
Somone who knows how I best handle this problem? I have tried to change the mode of the TCP read to CRLF but without succes

If you have 1MB if random binary data, is highly likely that there will be a CRLF embedded somewhere by chance, so that won't work. None of your vague comments and suggestions make any sense so far. This is most likely a very simple problem that you are way overthinking and trying to overengineer. Billions of bytes of variable lenght data are transmitted every second across the world and nobody else seems to have these problems.
Please be more specific about your application:
Where is the data coming from?
Is it also LabVIEW and do you have control over the sending program?
How easy is it to tell if it is binary or formatted?
Can you tell from the data pattern once an entire set is received?
how long are the pauses between datasets?
What happens to the data after it is received? (stream to disk, scan, parse, etc.)
LabVIEW Champion . Do more with less code and in less time .

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Reading unknown number of bytes !

Hi all !
I am trying to read unknown number of bytes from the socket.Meanwhile I need to process the bytes depending on the message type in the header.I get messages like this header,body,header,body header,body header,body.....the message type is specified in the header.Each message type has different body size.So depending on that I have to read the next few bytes from the socket....say 300 or 600 depending the on the message type in the header.I get the bytes continioulsy like this.Since I cannot read byte by byte due performance reason is there any other way to do that.....any help will appreciated
sash

A simple workaround is to use a java.io.PushbackInputStream
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Reading unkown number of bytes

Hi all !
I am trying to read unknown number of bytes from the socket.Meanwhile I need to process the bytes depending on the message type in the header.I get messages like this header,body,header,body header,body header,body.....the message type is specified in the header.Each message type has different body size.So depending on that I have to read the next few bytes from the socket....say 300 or 600 depending the on the message type in the header.I get the bytes continioulsy like this.Since I cannot read byte by byte due performance reason is there any other way to do that.....any help will appreciated
sash

Assuming you have a consistent header size and format, you can just read that in one call. I prefer sticking the size of body in the header. That way I can pluck that value out of the header and use it for the next read.

How to get the number of bytes at TCP port

Hi all,
How to get the number of bytes to read at the TCp port...as someone had suggested in some forum we do read the number of bytes first and then pass this...
but we get a problem when we have FF data in this...because then it sends 2 FF data...and cause of this we skip the last data...is there any solution for the same?

Hi
In LabVIEW you don't have the same property as in serail port.
You havn't "Byte at TCPIP port".
if you developp a protocol, one soltion, is to send the size to read.
Ingénieur d'Application / Développeur LabVIEW Certifié (CLD)
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TCP Read w/ #bytes=4 returns wrong data.

On an initial TCP Read to a just-open connection, I can read any number of bytes, always getting the first n bytes from the arriving data. Except when I try to read 4 bytes! Then I get 4 bytes, but they're the seventh through ninth bytes, not the first four. Haven't found any other number that gives problems - 1,2,3,5,6,7,8,16,40,1020,etc. all work fine. Ideas?

You may want to try runnig the Data Client and Data Server example VIs which ship with LabVIEW and see if they work on your system. The Client example actually reads in 4 bytes every time. I ran it and it works fine, so if yours exhibits the behavior you've been seeing, then the problem could be with your connection. Otherwise, if the example does work, then it could be somewhere in your code. Let us know what you find.
J.R. Allen

TCP/IP Read - How do I find the number of bytes available

It appears that this is not directly possible. I am trying to get around
this by doing a tcp/ip buffered read with a very short timeout (0 or 1ms).
In theory it seems like I should be able to keep making the read call until
the exact number of bytes (4 in this case) pops out. It mostly works but
every so often hangs for some period of time and then resumes getting the 4
byte packets. Anybody have any idea what is going on?

The first thing I'm thinking of is that your delay is too short. Also, try to increase the packet length or use Immediate Mode (even CRLF MODE if you're transmitting text).
Another idea (if your application really needs that and you have LV / Windows) is to use MS Winsock Control (wait for DataArrival event and read BytesReceived).
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Good luck!

How to get the number of bytes at ethernt port using tcp/ip?

I have data with variable sizes.I am getting the data from another sytem using software C.
How can I get the exact number of bytes coming at the port before using the read command so that the no. of bytes at port has to be given as the input to the tcp read vi?

Philippe_RSA wrote:
So may responses saying your question is wrong..... typical of this site, and no decent answer after 5 years !
The answer I have used is to use a call library function:
short int ioctlsocket(unsigned long socket, unsigned long fionread, unsigned long *len);
where fionread is a windows defined constant = 4004667F
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A protocol requiring such a hack is IMHO very poorly designed. You should always have some way on the wire to determine the data stream size. If the data is fixed size that would be inherent to the protocol, if it's variable sized there should be a fixed size header or a known message termination indication that can be used to determine how to read the rest of the message.
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Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

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Hi all,
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while ((str = in.readLine()) != null)
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Thanks

import javax.swing.*;
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How do I write and read a specified number of bytes using C++?

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Hey BMas05,
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National Instruments

ORA-27063: number of bytes read/written is incorrect

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I am getting this error because my filesytem is at 100%:
ORA-01114: IO error writing block to file 202 (block # 423324)
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Mike,
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Hello every one
I am getting this in my event log from time to time . not sure what is that ?
Is this a hacker trying to send rubbish data to SQL through the port ?
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Length specified in network packet payload did not match number of bytes read; the connection has been closed. Please contact the vendor of the client library. [CLIENT: someip]

Thank you all for the reply ,
my server is on port 1533 . Port 1433 is closed on my server .
All the requests are coming from my own ip , i feel this is funny .
Is my server hacked then ?
Or could be my ISP doing any routine tests ?
Also is this is hack attempt , what does this hacker think he will benefit from this ? Could this bring the SQL server down ?
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Error 56 in TCP Read

Hi,
I have TCP Read in a loop expecting data from some Micropchip boards connected to it. The problem I have is the boards do not send data all the time, hence I cannot wire in a specific constant to the number of bytes to read in, in the TCP read block.
Am I right in saying the only option is to clear the error 56 when it occurs?
Thanks,
Harshil

That should solve the problem. See this post...
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Now is the right time to use %^<%Y-%m-%dT%H:%M:%S%3uZ>T
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Inplaceness is synonymous with insidiousness

Modbus tcp read holding registers not returning requested quantity

Background: I have a customer using an ELAU motion system - they are recording data to Holding Registers that they want to be able to read on a cRIO to match up with some analog data from FPGA (I have digital handshaking happening for that).
LabVIEW 2010 SP1
cRIO 9074
Using the NI MOdbus.llb VI Library to communicate with the other system. I can open the TCP communication no problem, and actually get SOME registers, just not ALL of the register data I want to read.
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I provide the MB Ethernet Master Query (poly).vi with the starting address for the first register and then the quantity of 330. The polymorphic instance selected the is "Read Holding Registers". The array returned from this VI via "Holding Registers" is only 74 elements and not 330 requested. I get no exception codes and no LV errors. Is there some inherent limit on the number of Holding Registers that can be read?
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Thank you.
Ryan Vallieu
Automation System Architect
Solved!
Go to Solution.

Simple solution once I dug into the MODBUS Serial protocol/TCP protocol documentation available out there via Google.
Serial based modbus history is the limitation that carried over to TCP - the maximum amount of bytes in one data pack can only be 256 bytes. Thus I was limited to around ~125 registers at once.
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Ryan Vallieu
Automation System Architect

Output says "The number of bytes in the file are 0" but the file has bytes

Dear Java People,
Why would an output say a file has 0 bytes when upon doing a search for the file in Windows Explorer it say the file has 1 -4 kbytes ?
for example part of my output was :
"the number of bytes in TryFile3.java are 0"
caused by the following lines of code:
System.out.println("\n" + contents[i] + " is a " +
(contents.isDirectory() ? "directory" : "file\n") +
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+ "\nthe number of bytes in TryFile.java are " + myFile.length());
thank you in advance
below are the two program classes
Norman
import java.io.File;
import java.io.FilenameFilter;
import java.util.Date;
public class TryFile3
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+ "\nthe number of bytes in TryFile3.java are " + myFile.length());
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import java.io.FilenameFilter;
import java.util.Date;
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private String extension; // File extension filter
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this.extension = extension;
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System.out.println("\n" + contents + " is a " +
(contents.isDirectory() ? "directory" : "file\n") +
" last modified on " + new Date(contents.lastModified())
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TCP Read undifined number of bytes

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