Home » Tutorials » Tutorial 1 - creating IP fragment reassembler

Step 2 - setup the main class

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We are going to setup the main class as the packet handler as well. All it needs to do is implement the PcapPacketHandler interface. We are also going to use a static main method that will setup the libpcap portion and register our application as listener to libpcap packets.

public class IpReassemblyExample implements PcapPacketHandler {

  public static void main(String[] args) {
    StringBuilder errbuf = new StringBuilder();
    Pcap pcap = Pcap.openOffline("tests/test-ipreassembly2.pcap", errbuf);
    if (pcap == null) {
      System.err.println(errbuf.toString());
      return;
    }

    pcap.loop(
      6, // Collect 6 packets
      new IpReassemblyExample(
        5 * 1000, // 5 second timeout for reassembly buffer
        new IpReassemblyBufferHandler() {/*Omitted for now */}),
      "");
  }
}

Here we are using the static main method as a start for our application. We open up a capture file and enter a dispatch loop. We're only collecting 6 packets and we are registering out application as the PcapPacketHandler. Our constructor takes a IpReassemblyBufferHandler that will be notified with reassembled buffers. We create an anonymous class for that since we only do very minor work in its handler callback method.

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