core.py 文件源码

def send(sock, addr, id, size, seq=1):
    # Create an echo request
    icmp_type = 8
    icmp_code = 0
    icmp_chksum = 0
    icmp_id = id
    icmp_seq = seq

    header = struct.pack("bbHHh",
            icmp_type, icmp_code, icmp_chksum, icmp_id, icmp_seq)

    # The size of the packet must be large enough to accomodate the header and
    # a timestamp
    if size < struct.calcsize("bbHHhd"):
        raise PacketSizeError()

    # Create a chunk of data that is prepended by a timestamp so that we can
    # determine how long it takes the packet to return.
    timestamp = struct.pack("d", time.time())
    data = timestamp + os.urandom(size - struct.caclsize("bbHHhd"))

    # Now we can figure out the checksum
    icmp_chksum = socket.htons(checksum(header + data))

    # Construct the message using the checksum
    header = struct.pack("bbHHh",
            icmp_type, icmp_code, icmp_chksum, icmp_id, icmp_seq)
    packet = header + data

    # Send the request to the address
    host = socket.gethostbyname(addr)
    sock.sendto(packet, (host, 1))