how to send packet over UDP socket to controller

Hello,

i want to send packet which contain following data

header=0x1234(uint16); <---this is hex number

command=2(uint16) 

num_samples=1(uint32);

can anyone help how can i create packet

what i am doing is

my pc, ipA = '192.168.1.10'; portA = 49153;

ATI F/T sensor, ipB = '192.168.1.2'; portB = 49152;

udpA = udp(ipB,portB,'LocalPort',portA);

    fopen(udpA);

    request=zeros(1,3)%created array

    header = '0x1234';

    command= 2;

    num_samples = 1;

    a = char(header)

    b=command;

    c=num_samples;

    request(1,1)=int16(a)

    request(1,2)=int16(b)

    request(1,3)=int32(c)

    fwrite(udpA, request)

when i send this packet robot should start to send data to my pc

but i am not getting any data when i run fread(udpA) command.

here i had attached my C code file same functionality i would like to build in matlab

Answer 1

[Walter Roberson]

a = hex2dec(header);

request = [ typecast(int16([a, b]), 'uint8'), typecast(int32(c), 'uint8') ];

It is uncommon for commands or headers or counts to be signed integers. You should re-check whether they are really int16() and int32() or are instead uint16() and uint32()

[Lalji goti]

thank you for your valuable answer i think it will work but still i am getting problem when i am sending this packet and at receiving end converting this packet in hex than i am getting value like 34 12 02 00 01 00 00 00 but actually it should be 12 34 02 00 01 00 00 00

and as you said data type of variable is unsigned integers. you are right

when i am experimenting on matlab command window i am getting result which mentioned below

dec2bin(unt16([a, b]))

ans=

1001000110100 %this one is right 

0000000000010

dec2bin(typecast(uint16([a, b]), 'uint8'))

ans= 

110100

010010

000010

000000

[Walter Roberson]

Have a look at http://www.mathworks.com/help/matlab/ref/swapbytes.html

See also http://en.wikipedia.org/wiki/Endianness. In particular, by convention you should be using Network Byte Order to send multi-byte values.

See then http://www.mathworks.com/company/newsletters/articles/two-new-functions-for-converting-datatypes-and-changing-byte-order.html

[Lalji goti]

thank you very very very very very much finally it works....

this is my whole program

import java.net.*
import java.io.*
import com.atiia.automation.sensors.*
import java.net.DatagramSocket
import java.net.DatagramPacket
import java.net.InetAddress

clientSocket = DatagramSocket;
IPAddress = InetAddress.getByName('192.168.1.2');
port=49152;

header = '1234';

a=hex2dec(header);
a=uint16(a);
a=swapbytes(a);

command= 2;
b=command;
b=uint16(b);
b=swapbytes(b);

num_samples = 1;
c=num_samples;
c=uint32(c);
c=swapbytes(c);

request1= typecast(([a,b]), 'uint8');
request2= typecast([c], 'uint8');
request = [ request1,request2 ];

 i=0;
while (i<2)
try
    %request = [ typecast(([a, b]), 'uint8'), typecast(int32(c), 'uint8') ];
    request = [ request1,request2 ];
    socket = DatagramSocket;
    socket.setSoTimeout(1500);
    socket.connect( IPAddress, port);
    sendPacket = DatagramPacket(request, length(request), IPAddress, port);
    clientSocket.send(sendPacket);
catch sendPacketError
end
   try 
    packetLength=36; %total byte received from netFT
    receivePacket = DatagramPacket(zeros(1,packetLength,'uint8'),packetLength);
    clientSocket.receive(receivePacket);
    mssg = receivePacket.getData;
    fprintf(1, 'Received %d bytes\n', receivePacket.getLength)
    mssg = mssg(1:receivePacket.getLength);
    rdt_sequence = tyepcast(mssg(1:4), 'uint32')
    ft_sequence = tyepcast(mssg(5:8), 'uint32')
    status = tyepcast(mssg(9:12), 'uint32')

    Fx=typecast(mssg(13:16), 'uint32');
    Fy=typecast(mssg(17:20), 'uint32');
    Fz=typecast(mssg(21:24), 'uint32');
    Tx=typecast(mssg(25:28), 'uint32');
    Ty=typecast(mssg(19:32), 'uint32');
    Tz=typecast(mssg(33:36), 'uint32');

    fprintf(1, 'rdt_sequence: %d\n', rdt_sequence)
    fprintf(1, 'ft_sequence: %d\n', ft_sequence)
    fprintf(1, 'status: %d\n', status)
    fprintf(1, 'Fx: %d\n', Fx)
    fprintf(1, 'Fy: %d\n', Fy)
    fprintf(1, 'Fz: %d\n', Fz)
    fprintf(1, 'Tx: %d\n', Tx)
    fprintf(1, 'Ty: %d\n', Ty)
    fprintf(1, 'Tz: %d\n', Tz)

    inetAddress = receivePacket.getAddress;
    sourceHost = char(inetAddress.getHostAddress);
    fprintf(1, 'inetAddress: %s',sourceHost);
catch receiveError
end
end
clientSocket.close;

can i do such stuff by using simulink block....can u suggest me in simulink how can i make this packet??

[Walter Roberson]

I am aware that there is a UDP Simulink block, but I have never looked at it.

[Lalji goti]

here i am sending you my simulink file... i am trying to create same packet in simulink but i cant, can you tell me where i am doing mistake

[Walter Roberson]

Sorry, I do not have Simulink to experiment with. (Donations of software are accepted ;-) )

[Lalji goti]

yes, i will, send me your email id, i will send you link of my outbox so u can download it

[Lalji goti]

hello, i have one more question regarding my code which i had written above.

in matlab how can i stop my infinity loop.. when my cord start receiving data its not stop i have to close whole matlab if i want to stop infinity loop

[Walter Roberson]

The code is infinite because you are looping while i < 2 but you never change i.

You could assign a value >= 2 to "i", or you could use "break".

[Lalji goti]

Hello Walter Roberson,

how can i run two program parallel in matlab. means my one program getting position data continuously from robot. anotther program sending command in between first program is running..

data listening program

while 1
while ~(iStream.available)
end
 readS(iStream);
end

command sending program

while 1
    userInput = input('Server: ', 's');
    oStream.sendS(userInput);
end

how can i run this both infinite loop program parallel in matlab i want some commands to controller while datal listening infinite loop is runnig...

Plz Help me out

[Walter Roberson]

This has been answered in your Question that you created about it.