ping_class.py 文件源码

def send_one_ping(my_socket, dest_addr, ID):
    """
    Send one ping to the given >dest_addr<.
    """
    dest_addr  =  socket.gethostbyname(dest_addr)

    # Header is type (8), code (8), checksum (16), id (16), sequence (16)
    my_checksum = 0

    # Make a dummy heder with a 0 checksum.
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, my_checksum, ID, 1)  #?
    #a1 = struct.unpack("bbHHh",header)    #my test
    bytesInDouble = struct.calcsize("d")
    data = (192 - bytesInDouble) * "Q"
    data = struct.pack("d", time.time()) + data

    # Calculate the checksum on the data and the dummy header.
    my_checksum = checksum(header + data)

    # Now that we have the right checksum, we put that in. It's just easier
    # to make up a new header than to stuff it into the dummy.
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(my_checksum), ID, 1)
    packet = header + data
    my_socket.sendto(packet, (dest_addr, 1)) # Don't know about the 1