使用 JPOS 附加 2 个字节的十六进制长度两个 Iso8583 消息

Question

I am using JPOS to send a 0800.network request. But the problem is that header length of 2 bytes is not getting appended to my message. The length of the message if 42 but adding the header of 2 bytes should make it 44. TCP DUMP:

 length 42
        0x0000:  4500 005e 4448 4000 4006 8842 0a14 5140  E..^DH@.@..B..Q@
        0x0010:  0a5f 085d 952e 30c8 5cdb c683 49e6 692d  ._.]..0.\...I.i-
        0x0020:  8018 01f6 6e60 0000 0101 080a 0775 0600  ....n`.......u..
        0x0030:  889f a492 3038 3030 8220 0100 0000 0000  ....0800........
        0x0040:  0400 0000 0000 0000 3132 3234 3139 3035  ........12241905
        0x0050:  3136 3132 3033 3437 3030 3130 3033       16120347001003

Since my message is of 42 length, 002A should be append in hex dump.

The message should be:

My Code:
BaseChannel channel = new NACChannel(packager, null);
channel.setHost("xx.xx.xx.xx", xxxxx);
channel.connect();
ISOMsg isoMsg = new ISOMsg();
isoMsg.setPackager(packager);
isoMsg.setMTI("0800");
isoMsg.set(7, "1224190516");
isoMsg.set(11, "120347");
isoMsg.set(24, "001");
isoMsg.set(70, "003");
byte[] send_PackedRequestData = isoMsg.pack();
channel.send(send_PackedRequestData);

How can i append the length of the message to the start so it become

002A0800................1224190516120347001003

Answer 1

Use String.format("%04x%s", strIsoMsg.length()/2, strIsoMsg) .

I provide you a pattern code which you can use this pattern for sending message. the

   ISO87BPackager packager = new ISO87BPackager();

   ISOMsg isoMsg = new ISOMsg();
   isoMsg.setPackager(packager);
   isoMsg.setMTI("0800");
   isoMsg.set(3, "000000"); //PROCESSING CODE
   isoMsg.set(4, strAmount); //AMOUNT, TRANSACTION
   ...
   ...
   ...

   byte[] b1 = isoMsg.pack();
   isoMsg.set(64, MAC.calcMac(b1));
   byte[] b2 = isoMsg.pack();
   strIsoMsg = "700800900" + new String(Hex.encodeHex(b2));
   
   String msgHexWithLen = String.format("%04x%s",  strIsoMsg.length()/2, strIsoMsg);
   byte[] bytes = IsoParser.hexStringToByteArray(msgHexWithLen);
   ...
   ...
   ...
   Socket socket = new Socket();
   socket.connect(new InetSocketAddress("x.y.z.w", 7151), 5000);
   socket.setSoTimeout(30000);

   socket.getOutputStream().write(bytes, 0, bytes.length);
   socket.getOutputStream().flush();