Question

I am attempting to call two_byte_proc(payload,offset) from within process() but it does not write to the output file out_buf. The output from offset or payload may contain None so those iterations should be skipped and restart the process function with the next packet.

def process():
    pkts = sniff(offline="infile.pcap",filter="tcp")
    out_buf = open("outfile.bin","wb")

    for pkt in pkts:
        offset = hexdump(str(pkt.payload)[:2])
        payload = hexdump(pkt.payload)

        if offset or payload is None:
            pass
        else:
            out_buf.write(two_byte_proc(payload,offset))

process()

Answer 1

The expression offset or payload is None is always True; perhaps you meant:

if offset is None or payload is None:

instead.

Since you ‘pass’ if that expression is True, you may as well reverse it:

if offset is not None and payload is not None:
    out_buf.write(two_byte_proc(payload, offset))

I suspect that offset and payload are either strings with length > 0 or None, in which case that can be further simplified to:

if offset and payload:
    out_buf.write(two_byte_proc(payload, offset))

Last but not least, you need to make sure that two_byte_proc (or four_byte_proc after your edit) actually returns something to write to out_buf. If all it returns is an empty string, for example, you won’t see any results.