transfer doubles between java and simulink using udp

Question

I need to transfer decimal values between Java program and a Simulink model, to do so i use UDP sockets, they are no problem in the java side. In Simulink i am able to send the values using 'Stream Output' block, but the problem presents while receiving from java! the 'Stream input' block doesn't receive any thing. I am using standard devices UDP protocole, with the right Local UDP port and the address is 'localhost. Please tell me how to correctly receive a double in simulink with udp, or even with other methods, what matter is to transfer the data. thanks in advance. here are some code:

localSocket = new DatagramSocket(9010);

...

 public static void localSend(String msg,int PORT) throws Exception{  
    DatagramPacket sendPacket = null,encPacket=null;
    try {
        sendPacket = new DatagramPacket(msg.getBytes(), msg.getBytes().length, InetAddress.getLocalHost(), PORT);
    } catch (Exception e) {
        System.out.printf("Error!");
    }
    localSocket.send(sendPacket);
}

and in the main method:

localSend(myMessage, 9005);

the 'Board setup' of the 'Input Stream' block is Simulink is as below:

here is how i receive data from Simulink ins Java (the method):

    public static String localReceive() throws Exception{                     
     DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
     int count=0;
       try {
           localSocket.receive(receivePacket);
            return new String(receivePacket.getData(),receivePacket.getOffset(),receivePacket.getLength());
            } catch (SocketTimeoutException socketTimeoutException) {
                return defaultValue;
            }
 }

and the setup of "Output Stream" block in Simulink:

Isbell

you need to tell us your block parameter setups, are you sure that the port/address are all correct? – Rizo

ok, i will edit the question – Isbell

@nuser1955419 - Show us how are you sending data from Simulink, and the relevant Java code --- this much is insufficient to deduce an answer! – Varlet

i added it in an edit – Isbell

Answer 1

i did a trick. 'Packet Input' Simulink block, and 'ASCII Decode',

i adjust the parameters of these 2 blocks as follows:

and in the java side, i 'reformat' the double, with this method:

public static String reformat(String str){
    double d = 0;
    DecimalFormat df=null;
    try {
        d = Double.parseDouble(str);
    } catch (NumberFormatException numberFormatException) {
        return "0.00000";
    }
    if(d>=0){
    String[] sp=str.split("\\.");
    if(sp[0].length()==0)
    df= new DecimalFormat("0.00000");
    if(sp[0].length()==1)
    df= new DecimalFormat("0.00000");
    if(sp[0].length()==2)
        df= new DecimalFormat("00.0000");
    if(sp[0].length()==3)
        df= new DecimalFormat("000.000");
    if(sp[0].length()==4)
        df= new DecimalFormat("0000.00");
    if(sp[0].length()==5)
        df= new DecimalFormat("00000.0");
    }
    else{
    String[] sp=str.split("\\.");
    if(sp[0].length()==1)
    df= new DecimalFormat("0.0000");
    if(sp[0].length()==2)
    df= new DecimalFormat("0.0000");
    if(sp[0].length()==3)
        df= new DecimalFormat("00.000");
    if(sp[0].length()==4)
        df= new DecimalFormat("000.00");
    if(sp[0].length()==5)
        df= new DecimalFormat("0000.0");
    if(sp[0].length()==6)
        df= new DecimalFormat("000000");
    }

    try {
        return df.format(d);
    } catch (Exception e) {
        return "0.00000";
    }
}

briefly: the packet input block receives 7 ASCIIs each time, and in java i reformat the double to be combined of 7 characters (including the point and the minus).

Hope this help someone.

update:

some self explanatory extra code:

//somewhere before:
//Global variables
    String defaultValue="0",ip="xxx.xx.xx.xx";
    DatagramSocket remoteSocket,localSocket;
    byte[] receiveArray,receiveKey,receiveSig,sendSig;
    int remoteSendPort=xxx,localSendport=xxx,
        remoteReceivePort=xxx,localReceivePort=xxx;    
    String feedback,control_val,ReceivedTimeStamp;
    InetAddress IPAddress;     
...
//receive message from the other java program in pc2 
    public  void remoteMsgSend(byte[] msg,InetAddress IPAddress, int PORT)  {     
        try {     
            DatagramPacket sendPacket = null;
            try {
                sendPacket = new DatagramPacket(msg, msg.length, IPAddress, PORT);
            } catch (Exception e) {
                System.out.printf("Error! check ports");
            }
            remoteSocket.send(sendPacket);
        } catch (IOException ex) {
            System.out.println("IOException! remote send");
        }
    }
    //receive message from the other java program in pc2
    public  String remoteMsgReceive() {                     
         DatagramPacket receivePacket = new DatagramPacket(receiveArray, receiveArray.length);
         byte[] r1;
         int count=0,len,offset;
           try {
               remoteSocket.receive(receivePacket);
               r1=receivePacket.getData();
               len=receivePacket.getLength();
               offset=receivePacket.getOffset();
               r1=Arrays.copyOfRange(r1, offset, len);
               remoteOk=true;
                return new String(r1);
                } catch (Exception ex) {
//                    System.out.println("remote receive time out: " +ex.getMessage());
                    remoteOk=false;
                    return defaultValue;
                }
     }

    //send data to matlab on this pc
    public  void localSend(String msg,int PORT)  {  
        DatagramPacket sendPacket = null;
        try {
            sendPacket = new DatagramPacket(msg.getBytes(), msg.getBytes().length, InetAddress.getLocalHost(), PORT);
        } catch (Exception e) {
            System.out.printf("Error! check ports");
        }
        try {
            localSocket.send(sendPacket);
        } catch (IOException ex) {
            System.out.println("localsend error");
        }
    }
    //receive data from Matlab on this pc
    public  String localReceive() {                     
         DatagramPacket receivePacket = new DatagramPacket(receiveArray, receiveArray.length);

         String rec;
           try {
               localSocket.receive(receivePacket);
               rec=new String(receivePacket.getData(),receivePacket.getOffset(),receivePacket.getLength());
               localOk=true;
                return rec;
                } catch (Exception ex) {
//                          System.out.println("local receive time out " +ex.getMessage());
                          localOk=false;
                          return defaultValue;
                }
     }

Isbell

Can you please show the code for this answer? I have a very similar problem and I am using the same blocks but I simply cant receive the data from the pc running to the matlab pc. – Wader

Hello @Flower, sorry i were offline for a while. first ensure that your connection is well established (no firewalls, good ports...) you can use a software to test it like linkPacketSended. i will put my the requested code in an update. (btw, my second answer was better to solve the problem described in the question) – Isbell

There is no need to put your code in an update. I was able to get it working. Thanks so much, you answer helped me a lot. – Wader

yr welcome, i putted it before reading your comment. glade i can help. – Isbell

Answer 2

Another solution, with the stream input in Simulink. Just add a terminator "\n" to each message from java.

Isbell