繼上一篇計算checksum校驗和，本章通過socket套接字，struct位元組打包成二進位制，select返回套接字的檔案描述符的結合，實現一個簡單的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):
    """
    校驗
    """
    n = len(data)
    m = n % 2
 

    sum = 0 
    for i in range(0, n - m ,2):
        sum += (data[i]) + ((data[i+1]) << 8)#傳入data以每兩個位元組（十六進位制）通過ord轉十進位制，第一位元組在低位，第二個位元組在高位
    if m:
        sum += (data[-1])
    #將高於16位與低16位相加
    sum = (sum >> 16) + (sum & 0xffff)
    sum += (sum >> 16) #如果還有高於16位，將繼續與低16位相加
 

    answer = ~sum & 0xffff
    #主機位元組序轉網路位元組序列（參考小端序轉大端序）
    answer = answer >> 8 | (answer << 8 & 0xff00)
    return answer 

    '''
    連線套接字,並將資料傳送到套接字
    '''
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):
    #把位元組打包成二進位制資料
    imcp_packet = struct.pack('>BBHHH32s',data_type,data_code,data_checksum,data_ID,data_Sequence,payload_body)
    icmp_chesksum = chesksum(imcp_packet)#獲取校驗和
    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

    '''
    實現 ping 主機/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)#將主機名轉ipv4地址格式，返回以ipv4地址格式的字串，如果主機名稱是ipv4地址，則它將保持不變
    print("正在 Ping {0} [{1}] 具有 32 位元組的資料:".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("來自 {0} 的回覆: 位元組=32 時間={1}ms".format(addr,int(times*1000)))
            time.sleep(0.7)
        else:
            print("請求超時。")

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 位元組的資料:
來自 47.95.164.112 的回覆: 位元組=32 時間=39ms
來自 47.95.164.112 的回覆: 位元組=32 時間=40ms
來自 47.95.164.112 的回覆: 位元組=32 時間=40ms
來自 47.95.164.112 的回覆: 位元組=32 時間=39ms