public class tcp extends packet {
		
	int sourcePort = 0;              // Quellport-Nr.
	int destPort = 0;                // Zielport-Nr.
        long seqNo = 0;                  // SYN-Sequenznummer
        long ackNo = 0;                  // ACK-Sequenznummer
        int dataOffset = 0;              // Payload-Offset
	boolean syn = false;             // Verbindungsflags
	boolean ack = false;
	boolean fin = false;
        int window = 0;                  // TCP-Fensterindex
        int checksum = 0;                // Paketchecksumme
        String payload = new String();   // Daten
        

	public tcp(ip ipPacket, byte b[]) {
		
        	int position = ipPacket.getPayloadOffset();
        	
                // Parsing entsprechend RFC 793, siehe [4]
        
        	sourcePort = getWord(position,b);
        	position+=2;
        	destPort = getWord(position,b);
        	
        	position+=2;
                seqNo = getLong(position,b);
        	position+=4;
                ackNo = getLong(position,b);
                
                position+=4;
                dataOffset = (getByte(position,b) & 0xF0) >> 4;
        
        	position++;
        	syn = (getByte(position,b) & 0x02) == 0x02 ? true : false;
        	ack = (getByte(position,b) & 0x10) == 0x10 ? true : false;
        	fin = (getByte(position,b) & 0x01) == 0x10 ? true : false;
        	
        	window = getWord(++position,b);
        	checksum = getWord(++position,b);
        	
        	int payloadBegin = ipPacket.getPayloadOffset() + dataOffset*4;
        	int payloadLength = ipPacket.getLength() - payloadBegin;
        	if (payloadLength > 0) {
        	        payload = new String(b, payloadBegin, payloadLength);
        	} else {
        	        payload = "<empty>";
        	}
        }
        
        public String headerString() {
                String packetString = new String("Source port: "+sourcePort+"\nDestination Port: "+destPort);
                packetString += "\nSequence No: "+seqNo+"\nAck No: "+ackNo;
                packetString += "\nSYN: "+syn+"  ACK: "+ack+"  FIN:"+fin;
                packetString += "\nWindow: "+window;
                packetString += "\nData Offset: "+dataOffset;
		return packetString;
        }

        public String payloadString() {
		return payload;
        }
}