python实现一个简单的ping工具方法

继上一篇计算checksum校验和，本章通过socket套接字，struct字节打包成二进制，select返回套接字的文件描述符的结合，实现一个简单的ping工具。

#!/usr/bin/python3.6.4
#!coding:utf-8
__author__ = 'Rosefinch'
__date__ = '2018/5/31 22:27'

import time
import struct
import socket
import select
import sys

def chesksum(data):
  """
  校验
  """
  n = len(data)
  m = n % 2
  sum = 0 
  for i in range(0, n - m ,2):
    sum += (data[i]) + ((data[i+1]) << 8)#传入data以每两个字节（十六进制）通过ord转十进制，第一字节在低位，第二个字节在高位
  if m:
    sum += (data[-1])
  #将高于16位与低16位相加
  sum = (sum >> 16) + (sum & 0xffff)
  sum += (sum >> 16) #如果还有高于16位，将继续与低16位相加
  answer = ~sum & 0xffff
  #主机字节序转网络字节序列（参考小端序转大端序）
  answer = answer >> 8 | (answer << 8 & 0xff00)
  return answer 

  '''
  连接套接字,并将数据发送到套接字
  '''
def raw_socket(dst_addr,imcp_packet):
  rawsocket = socket.socket(socket.AF_INET,socket.SOCK_RAW,socket.getprotobyname("icmp"))
  send_request_ping_time = time.time()
  #send data to the socket
  rawsocket.sendto(imcp_packet,(dst_addr,80))
  return send_request_ping_time,rawsocket,dst_addr

  '''
  request ping
  '''
def request_ping(data_type,data_code,data_checksum,data_ID,data_Sequence,payload_body):
  #把字节打包成二进制数据
  imcp_packet = struct.pack('>BBHHH32s',data_type,data_code,data_checksum,data_ID,data_Sequence,payload_body)
  icmp_chesksum = chesksum(imcp_packet)#获取校验和
  imcp_packet = struct.pack('>BBHHH32s',data_type,data_code,icmp_chesksum,data_ID,data_Sequence,payload_body)
  return imcp_packet
  '''
  reply ping
  '''
def reply_ping(send_request_ping_time,rawsocket,data_Sequence,timeout = 2):
  while True:
    started_select = time.time()
    what_ready = select.select([rawsocket], [], [], timeout)
    wait_for_time = (time.time() - started_select)
    if what_ready[0] == []: # Timeout
      return -1
    time_received = time.time()
    received_packet, addr = rawsocket.recvfrom(1024)
    icmpHeader = received_packet[20:28]
    type, code, checksum, packet_id, sequence = struct.unpack(
      ">BBHHH", icmpHeader
    )
    if type == 0 and sequence == data_Sequence:
      return time_received - send_request_ping_time
    timeout = timeout - wait_for_time
    if timeout <= 0:
      return -1

  '''
  实现 ping 主机/ip
  '''
def ping(host):
  data_type = 8 # ICMP Echo Request
  data_code = 0 # must be zero
  data_checksum = 0 # "...with value 0 substituted for this field..."
  data_ID = 0 #Identifier
  data_Sequence = 1 #Sequence number
  payload_body = b'abcdefghijklmnopqrstuvwabcdefghi' #data
  dst_addr = socket.gethostbyname(host)#将主机名转ipv4地址格式，返回以ipv4地址格式的字符串，如果主机名称是ipv4地址，则它将保持不变
  print("正在 Ping {0} [{1}] 具有 32 字节的数据:".format(host,dst_addr))
  for i in range(0,4):
    icmp_packet = request_ping(data_type,data_code,data_checksum,data_ID,data_Sequence + i,payload_body)
    send_request_ping_time,rawsocket,addr = raw_socket(dst_addr,icmp_packet)
    times = reply_ping(send_request_ping_time,rawsocket,data_Sequence + i)
    if times > 0:
      print("来自 {0} 的回复: 字节=32 时间={1}ms".format(addr,int(times*1000)))
      time.sleep(0.7)
    else:
      print("请求超时。")

if __name__ == "__main__":
  if len(sys.argv) < 2:
    sys.exit('Usage: ping.py <host>')
  ping(sys.argv[1])

>python .\Ping_tool.py www.csdn.net
正在 Ping www.csdn.net [47.95.164.112] 具有 32 字节的数据:
来自 47.95.164.112 的回复: 字节=32 时间=39ms
来自 47.95.164.112 的回复: 字节=32 时间=40ms
来自 47.95.164.112 的回复: 字节=32 时间=40ms
来自 47.95.164.112 的回复: 字节=32 时间=39ms

引用：

https://docs.python.org/3/library/socket.html

https://docs.python.org/3/library/select.html#select.select

https://docs.python.org/3/library/struct.html

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