import threadingimport timefrom netaddr import IPNetwork,IPAddress--snip--#监听的主机host = "192.168.0.187"#扫描的目标子网subnet = "192.168.0.0/24"#自定义的字符串，我们将在ICMP相应中进行核对。magic_message = "PYTHONRULE!"#批量发送UDP数据包def udp_sender(subnet,magic_message):    time.sleep(5)    sender = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)    for ip in IPNetwork(subnet):        try:            sender.sendto(magic_message,("%s") % ip,65212)        except:            passt = threading.Thread(target=udp_sender,args=(subnet,magic_message))t.start()--snip--try:    while True:        --snip--        #print "ICMP --> TYPE： %d Code: %d (icmp_header.type,icmp_header.code)        #检查类型和代码值是否为3        if icmp_header.code == 3 and icmp_header.type==3:            #确认相应的主机在我们目标子网之内            if IPAddress(ip_header.src_address) in IPNetwork(subnet):                if raw_buffer[len(raw_buffer)-len(magic_message):]==magic_message                    print "Host up:%s" % ip_header.src_address.