my jpos ISO8583 implementation keeps prefixing "1" to the message length

Question

My ISO JPOS client implementation prints message length output correctly but when I do tcpdump i see the message length prefixed with "1". So the tcpdump shows the message header as "10000431804003001000000000084946520200922160158801" instead of "0000431804003001000000000084946520200922160158801"

Any idea what could be the issue.

Below is my client print out of the message length and the unpack ISO: 0000431804003001000000000084946520200922160158801

<log realm="post-channel/xx.xx.xx.x:xxxx" at="Tue Sep 22 16:01:58 WAT 2020.579" lifespan="1ms">
  <send>
    <isomsg direction="outgoing">
      <!-- org.jpos.iso.packager.GenericPackager[deploy/cfg/customizedPackager.xml] -->
      <header>303030303433</header>
      <field id="0" value="1804"/>
      <field id="11" value="849465"/>
      <field id="12" value="20200922160158"/>
      <field id="24" value="801"/>
    </isomsg>
  </send>
</log>

my code implementation below:

            Date currDate = new Date();
            SimpleDateFormat lda = new SimpleDateFormat("yyyyMMddHHmmss", Locale.getDefault());
            String d = lda.format(currDate);
        
            QMUX mux1 = (QMUX) NameRegistrar.getIfExists("mux.pesa-link-mux");
            LoggingUtil.logDebugInfo("SIGNON MUX: " + mux1.getName());
            Random randomGenerator = new Random();
            int randomInt = randomGenerator.nextInt(1000000);
            String formatedInt;
            formatedInt = String.format("%06d", randomInt);
            ISOMsg m = new ISOMsg();
            //m.setHeader("000043".getBytes());
            ISOPackager p = new GenericPackager("/usr/app/customized.xml");
            byte[] b = new byte[1];
            m.setPackager(p);
            m.setMTI("1804");
            m.set(11, formatedInt);
            m.set(12, d);
            m.set(24, "801");

            byte[] data = m.pack();
            short messageLength = (short) data.length;
            String msglen = String.format("%6s", String.valueOf(messageLength)).replace(' ', '0');
            String message = msglen + new String(data);
            LoggingUtil.logDebugInfo(":: message length :: " + message + " :: len: " + msglen);
            ISOMsg resp = mux1.request(m, 30 * 1000);

channel config here

<channel-adaptor name="pd-channel-adaptor" class="org.jpos.q2.iso.ChannelAdaptor" logger="Q2">
     <channel class="org.jpos.iso.channel.PostChannel" type="client" connect="yes" logger="Q2"
             realm="post-channel" packager="org.jpos.iso.packager.GenericPackager">
            <property name="packager-config" value="deploy/cfg/customized.xml" />
<property name="host" value="1111.11.11.11" />
<property name="port" value="3322" />


    </channel>
    <in>pd_link_send</in>
    <out>pd_link_receive</out>
    <reconnect-delay>1000</reconnect-delay>
        <keep-alive>yes</keep-alive>
</channel-adaptor>

Answer 1

It seems your server is expecting the length as 6 ASCII digits, so you need to use ASCIIChannel with property length-digits set to 6

<channel-adaptor name="pd-channel-adaptor" class="org.jpos.q2.iso.ChannelAdaptor" logger="Q2">
     <channel class="org.jpos.iso.channel.ASCIIChannel" type="client" connect="yes" logger="Q2"
             realm="post-channel" packager="org.jpos.iso.packager.GenericPackager">
            <property name="packager-config" value="deploy/cfg/customized.xml" />
<property name="host" value="1111.11.11.11" />
<property name="port" value="3322" />
<property name="length-digits" value="6"/>

    </channel>
    <in>pd_link_send</in>
    <out>pd_link_receive</out>
    <reconnect-delay>1000</reconnect-delay>
        <keep-alive>yes</keep-alive>
</channel-adaptor>

And you don't have to put the length in the header.