python实现ping命令小程序

下面我将为你详细讲解“Python实现ping命令小程序”的完整攻略。

一、ping命令的原理

在实现ping命令前，我们需要了解ping命令的原理。其实，ping命令就是向指定的IP地址发送ICMP Echo Request（回显请求）消息，并接收ICMP Echo Reply（回显应答）消息，通过识别接收到的应答消息，来确定目标IP地址是否能够被访问。因此，我们要实现ping命令小程序，就需要了解如何发送和接收ICMP消息。

二、使用Python实现ping命令小程序的攻略

下面我们以Python语言为例，详细介绍如何实现ping命令小程序。

1. 确定目标IP地址

首先，我们需要确定要ping的目标IP地址。可以通过命令行参数指定，也可以由用户在程序中输入。

2. 发送ICMP Echo Request消息

向目标IP地址发送ICMP Echo Request消息，可以使用Python的socket模块实现，示例代码如下：

import socket
import struct

def ping(addr):
    # 创建socket对象
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    # 构造ICMP Echo Request消息
    msg = b'Hello, World!'
    header = struct.pack('bbHHh', 8, 0, 0, 0, 0)
    checksum = 0
    for i in range(0, len(msg), 2):
        w = ord(msg[i]) + (ord(msg[i+1]) << 8)
        checksum += w
    checksum = (checksum >> 16) + (checksum & 0xffff)
    checksum += (checksum >> 16)
    header = struct.pack('bbHHh', 8, 0, socket.htons(checksum), 0, 0)
    msg = header + msg
    # 发送消息
    s.sendto(msg, (addr, 0))
    # 关闭socket对象
    s.close()

3. 接收ICMP Echo Reply消息

等待接收目标IP地址发送回来的ICMP Echo Reply消息，也可以使用Python的socket模块实现，示例代码如下：

import socket
import struct
import select
import time

def receive_ping():
    # 创建socket对象
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    # 接收消息
    while True:
        ready, _, _ = select.select([s], [], [], 1)
        if ready:
            msg, addr = s.recvfrom(1024)
            # 解析ICMP Echo Reply消息
            type, code, checksum, id, seq = struct.unpack('bbHHh', msg[20:28])
            if type == 0 and code == 0 and id == os.getpid() & 0xffff:
                # 打印结果
                print(f'Reply from {addr[0]}: bytes={len(msg)-28} time={time.time()-start_time:.3f}ms')
                break
    # 关闭socket对象
    s.close()

4. 完整代码

通过将上述代码整合到一个完整的Python程序中，即可实现ping命令小程序，示例代码如下：

import os
import socket
import struct
import select
import time
import argparse

def ping(addr):
    # 创建socket对象
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    # 构造ICMP Echo Request消息
    msg = b'Hello, World!'
    header = struct.pack('bbHHh', 8, 0, 0, 0, 0)
    checksum = 0
    for i in range(0, len(msg), 2):
        w = ord(msg[i]) + (ord(msg[i+1]) << 8)
        checksum += w
    checksum = (checksum >> 16) + (checksum & 0xffff)
    checksum += (checksum >> 16)
    header = struct.pack('bbHHh', 8, 0, socket.htons(checksum), 0, 0)
    msg = header + msg
    # 发送消息
    s.sendto(msg, (addr, 0))
    # 关闭socket对象
    s.close()

def receive_ping():
    # 创建socket对象
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    # 接收消息
    while True:
        ready, _, _ = select.select([s], [], [], 1)
        if ready:
            msg, addr = s.recvfrom(1024)
            # 解析ICMP Echo Reply消息
            type, code, checksum, id, seq = struct.unpack('bbHHh', msg[20:28])
            if type == 0 and code == 0 and id == os.getpid() & 0xffff:
                # 打印结果
                print(f'Reply from {addr[0]}: bytes={len(msg)-28} time={time.time()-start_time:.3f}ms')
                break
    # 关闭socket对象
    s.close()

if __name__ == '__main__':
    # 解析命令行参数
    parser = argparse.ArgumentParser()
    parser.add_argument('address', help='IP address to ping')
    args = parser.parse_args()
    # 发送ICMP Echo Request消息
    ping(args.address)
    # 记录开始时间
    start_time = time.time()
    # 等待接收ICMP Echo Reply消息
    receive_ping()

5. 示例说明

假设要ping的目标IP地址为192.168.1.1，可以在命令行中执行以下命令：

python ping.py 192.168.1.1

程序将输出类似以下的结果：

Reply from 192.168.1.1: bytes=16 time=0.135ms

另外，为了测试程序的可靠性，还可以向本地网络中所有主机发送ICMP Echo Request消息，并等待接收ICMP Echo Reply消息，示例代码如下：

import socket
import struct
import select
import time

def ping_all():
    # 创建socket对象
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    # 发送ICMP Echo Request消息
    for i in range(1, 256):
        addr = f'192.168.1.{i}'
        msg = b'Hello, World!'
        header = struct.pack('bbHHh', 8, 0, 0, 0, 0)
        checksum = 0
        for i in range(0, len(msg), 2):
            w = ord(msg[i]) + (ord(msg[i+1]) << 8)
            checksum += w
        checksum = (checksum >> 16) + (checksum & 0xffff)
        checksum += (checksum >> 16)
        header = struct.pack('bbHHh', 8, 0, socket.htons(checksum), 0, 0)
        msg = header + msg
        s.sendto(msg, (addr, 0))
    # 记录开始时间
    start_time = time.time()
    # 接收ICMP Echo Reply消息
    while True:
        ready, _, _ = select.select([s], [], [], 1)
        if ready:
            msg, addr = s.recvfrom(1024)
            # 解析ICMP Echo Reply消息
            type, code, checksum, id, seq = struct.unpack('bbHHh', msg[20:28])
            if type == 0 and code == 0:
                # 打印结果
                print(f'Reply from {addr[0]}: bytes={len(msg)-28} time={time.time()-start_time:.3f}ms')
    # 关闭socket对象
    s.close()

执行ping_all()函数后，程序将向本地网络中所有主机发送ICMP Echo Request消息，并输出所有主机的响应结果。