This post talks about ways of sending Long message using SMPP

Using SMPP we can send long SMS by two means

Using Payload option

Submit SM PDU has a field called message_payload. Set the data in it and you can send upto 64K octets. But this option is not supported by a lot of provider. Verify with your provider, if they support the same.

Using Message fragementation

This format is more common and widely supported. Essentially, the long SMS is divided into smaller messages and send with a particular format, by setting UDH.

The key TLV options used are

sar_msg_ref_num - The reference number for a particular concatenated short message

sar_total_segments - Indicates the total number of short messages within the concatenated short message

sar_segment_seqnum - Indicates the sequence number of a particular short message fragment within the concatenated short message

How do you set these, depends upon the SMPP library you use. Will brief the algo

• Break the long sms into parts, so that fragement can fit into single Submit SM PDU
• The total number of fragements shall give the value of sar_total_segments
• Generate a unique identifier value, this becomes the values of sar_msg_ref_num
• Now in a loop send the message fragements, with values in step above. sar_segment_seqnum values shall be the value of the loop count (ensure that it starts from 1)

This is it

Pre-requisite

•  SNMP4J
•  Log4j

Structure

For complete source have a look at the class org.snmp4j.test. MultiThreadedTrapReceiver.java shipped with SNMP4J distribution

Logical structure of the program

• Create Socket for accepting Traps
• Create a Thread pool to process PDU’s
• Process the Traps

Let’s get into the code

Lets address the Listener creation steps

private void init() throws UnknownHostException, IOException {
 
    threadPool = ThreadPool.create("Trap", 2);
 
    dispatcher = MultiThreadedMessageDispatcher(threadPool,
                                           new MessageDispatcherImpl());
 
    listenAddress = GenericAddress.parse(System.getProperty("snmp4j.listenAddress",
                                                "udp:0.0.0.0/162"));
 
    TransportMapping transport;
 
    if (listenAddress instanceof UdpAddress) {
      transport = new DefaultUdpTransportMapping((UdpAddress)listenAddress);
    } else {
      transport = new DefaultTcpTransportMapping((TcpAddress)listenAddress);
    }
 
    snmp = new Snmp(dispatcher, transport);
    snmp.getMessageDispatcher().addMessageProcessingModel(new MPv1());
    snmp.getMessageDispatcher().addMessageProcessingModel(new MPv2c());
    snmp.getMessageDispatcher().addMessageProcessingModel(new MPv3());
 
    USM usm = new USM(SecurityProtocols.getInstance(),
                      new OctetString(MPv3.createLocalEngineID()), 0);
    SecurityModels.getInstance().addSecurityModel(usm);
    snmp.listen();
  }

Here we see that we have created Transport mapping to Listener on port 162. Next we add all three Message processing models, so that we can process Traps received from all three versions of SNMP (V1, V2C and V3). For SNMPv3, we add a Security model.

That’s it done. We listen and process the traps.

The default implementation of processPdu() in this class, just dumps some statistics on the output.

Customization’s

Let’s see what all can we do with this default example

• Set only the SNMP version you want to support
• Customize the Security Model for SNMP V3
• The whole logic lies on processPDU(). You can take complete control of how to process the message and subsequent processing of the message like dumping it to database etc.