Tcpdump using Jpcap

[Dicky Januari]

hii, everybody how are you ?

import jpcap.*;
import jpcap.packet.Packet;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.util.*;
import java.sql.*;
 
class Test {
    public static void main(String[] args) throws Exception {
        NetworkInterface[] devices = JpcapCaptor.getDeviceList();
 
        if(args.length<1){
            System.out.println("usage: java Tcpdump <select a number from the following>");
 
            for (int i = 0; i < devices.length; i++) {
                System.out.println(i+" :"+devices[i].name + "(" + devices[i].description+")");
                System.out.println("    data link:"+devices[i].datalink_name + "(" + devices[i].datalink_description+")");
                System.out.print("    MAC address:");
                for (byte b : devices[i].mac_address)
                    System.out.print(Integer.toHexString(b&0xff) + ":");
                System.out.println();
                for (NetworkInterfaceAddress a : devices[i].addresses)
                    System.out.println("    address:"+a.address + " " + a.subnet + " " + a.broadcast);
            }
        }else{
            JpcapCaptor jpcap = JpcapCaptor.openDevice(devices[Integer.parseInt(args[0])], 65535, true, 0);
            jpcap.setFilter("ip and tcp", true);
 
            for (int i = 0; i < 1000; i++) { 
                while (jpcap.getPacket() != null) {
                    Packet prot2 = jpcap.getPacket();
 
                    byte[] d = prot2.data;
                    byte[] h = prot2.header;
 
                    String p = new String(d);
                        System.out.println("");
 
                    for(byte b: d) {
                        System.out.print(Integer.toString(b, 16).toUpperCase());
                    } 
 
                    System.out.println("");
                    System.out.println("String form header:" + h);
                    System.out.println("");
                    String ss = prot2.toString();
 
                    if(prot2==null){
                        continue;
                    }
 
                    if(ss.contains("protocol(6)")){
                        System.out.println("Received packet TCP :" + jpcap.getPacket());
                    }
                 }
            }
        }
    }
}
 

guys the problem i have back there already solve, now with the code i post above i success build a simple tcpdump + reading packet header and payload...
now i want to try analysis the payload and header.. but don't know where i must start...
i'll appreciate who ever that told me where i must start..Thanks