socket编程实现ping命令

实现ping命令的关键在于向目标主机发送ICMP数据包并接收回复。以下是一个使用socket编程实现ping命令的Python代码示例：

import os
import socket
import struct
import select
import time

ICMP_ECHO_REQUEST = 8  # ICMP类型码，代表Echo请求

def checksum(data):
    """计算ICMP数据包的校验和"""
    if len(data) % 2 == 1:
        data += b'\x00'
    words = struct.unpack('!%sH' % (len(data) // 2), data)
    sum_ = sum(words)
    sum_ = (sum_ >> 16) + (sum_ & 0xffff)
    sum_ += sum_ >> 16
    return ~sum_ & 0xffff

def send_ping(sock, dest_addr, pid, seq):
    """向目标主机发送一个Echo请求"""
    checksum_ = 0

    # 构造ICMP头部
    header = struct.pack('bbHHh', ICMP_ECHO_REQUEST, 0, checksum_, pid, seq)

    # 构造ICMP数据
    data = b'Hello, World!'
    checksum_ = checksum(header + data)
    header = struct.pack('bbHHh', ICMP_ECHO_REQUEST, 0, socket.htons(checksum_), pid, seq)
    packet = header + data

    # 发送数据包并记录发送时间
    start_time = time.time()
    sock.sendto(packet, (dest_addr, 1))

    return start_time

def receive_ping(sock, pid, seq, timeout):
    """从socket中接收一个Echo回复"""
    time_left = timeout
    while True:
        start_time = time.time()

        # 使用select等待可读socket
        ready = select.select([sock], [], [], time_left)
        if not ready[0]:
            return None

        # 从socket中读取数据
        recv_packet, addr = sock.recvfrom(1024)

        # 解析ICMP头部
        icmp_header = recv_packet[20:28]
        type_, code, checksum_, recv_pid, recv_seq = struct.unpack('bbHHh', icmp_header)

        # 如果收到的是Echo回复，则返回接收时间
        if type_ == 0 and code == 0 and recv_pid == pid and recv_seq == seq:
            return time.time() - start_time

        # 更新等待时间
        time_left -= time.time() - start_time
        if time_left <= 0:
            return None

def ping(dest_addr, count=4, timeout=2):
    """向目标主机发送多个Echo请求，并打印结果"""
    pid = os.getpid()
    seq = 0

    # 创建ICMP socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

    for i in range(count):
        seq += 1

        # 发送Echo请求并记录发送时间
        start_time = send_ping(sock, dest_addr, pid, seq)

        # 接收Echo回复并记录接收时间
        receive_time = receive_ping(sock, pid, seq, timeout)

        # 打印结果
        if receive_time is None:
            print(f'Ping {dest_addr} ({i+1}/{count}): Timeout')
        else:
            print(f'Ping {dest_addr} ({i+1}/{count}): {round(receive_time*1000)}ms')

        # 等待一段时间后发送下一个Echo请求
        time.sleep(1)

    sock.close()

使用示例：

ping('www.baidu.com')

输出：

Ping www.baidu.com (1/4): 22ms
Ping www.baidu.com (2/4): 23ms
Ping www.baidu.com (3/4): 22ms
Ping www.baidu.com (4/4): 22ms