public class packetGrabber {

        public static final int netmask = 0xFFFFFF00;
        public static final int bufferSize = 2000;
        
        static final boolean detailed = false;

        static ip ipPacket;
        static tcp tcpPacket;
        static javacap jp;
        static byte[] packetBuffer;

        
	public static void check_error(javacap pcap) {
		String buffer = pcap.getError();
		if(buffer.length()>0){
                	System.out.println("pcap error: "+buffer);
                        System.exit(1);
                }
        }


        public static void main(String argv[]) {

                javacap pcap = new javacap();
                if (argv.length>0) { 
                        pcap.open(argv[0],bufferSize);
                        if (argv.length>1) {
                                String filterString = new String(argv[1]);
                                if (pcap.setFilter(filterString, netmask) == 0) {
                        	        System.out.println("Using filter: "+filterString);
                        	} else {
                                        System.out.println("Invalid filter rule: "+filterString);
                                }
                        }
                } else {
                        System.out.println("usage: packetGrabber interface [filterstring]");
                        System.exit(1);
                }


                packetBuffer = new byte[bufferSize];
                int dlt = pcap.getDataLinkType();

                System.out.println("Waiting for packets...");

                for(int anzahl=1;anzahl<100;anzahl++) {

                        pcap.read(packetBuffer);
                        check_error(pcap);
                        ipPacket = new ip(packetBuffer,dlt);

                        if(detailed){
                        	System.out.println("\n\nNr."+anzahl);
                        	System.out.println(ipPacket.headerString());
                        }

                        if (ipPacket.protocol == 6) {
                                tcp tcpPacket = new tcp(ipPacket,packetBuffer);
                                if(detailed){
	                                System.out.println("\nPayload contains TCP:");
	                                System.out.println(tcpPacket.headerString());
	                                System.out.println(tcpPacket.payloadString());
				}else if(!tcpPacket.payloadString().equals("<empty>")){
	                        	System.out.println();
	                                System.out.println(tcpPacket.payloadString());
                               	}
                        } else {
                                System.out.println("Unknown payload protocol");
                        }
                }
                pcap.close();
        }
}