计网课设1、课题1：Ping（网络层程序设计，必做） （1）Ping后不加参数实现四次ping。 （2）Ping后增加“-t”参数实现无限次ping。 （3）开发语言为python。

好的，那么以下是一个Python实现的Ping程序的示例代码，可以实现四次Ping和无限次Ping的功能：

import os
import sys
import struct
import time
import select
import socket

def checksum(data):
    n = len(data)
    m = n % 2
    sum = 0
    for i in range(0, n-m, 2):
        sum += (data[i]) + ((data[i+1])<<8)
    if m:
        sum += (data[-1])
    sum = (sum >> 16) + (sum & 0xffff)
    sum += (sum >> 16)
    result = ~sum & 0xffff
    result = result >> 8 | (result << 8 & 0xff00)
    return result

def ping(host, count=4, timeout=2, infinite=False):
    icmp = socket.getprotobyname("icmp")
    try:
        with socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp) as sock:
            sock.settimeout(timeout)
            # create packet
            packet_id = os.getpid() & 0xFFFF
            packet_seq = 1
            header = struct.pack("bbHHh", 8, 0, 0, packet_id, packet_seq)
            bytes_in_double = struct.calcsize("d")
            data = (192 - bytes_in_double) * "Q"
            data = struct.pack("d", time.time()) + bytes(data.encode("utf-8"))
            chksum = checksum(header + data)
            header = struct.pack("bbHHh", 8, 0, chksum, packet_id, packet_seq)
            packet = header + data

            while count > 0 or infinite:
                # send packet
                sent_time = time.time()
                sock.sendto(packet, (host, 1))
                count -= 1

                # receive packet
                try:
                    ready = select.select([sock], [], [], timeout)
                    if not ready[0]:
                        print("Request timed out.")
                        continue
                    recv_packet, addr = sock.recvfrom(1024)
                    recv_time = time.time()
                    delay = round((recv_time - sent_time) * 1000, 2)
                    print(f"Reply from {addr[0]}: bytes={len(recv_packet)} time={delay}ms")
                except socket.timeout:
                    print("Request timed out.")
                    continue

                packet_seq += 1
                header = struct.pack("bbHHh", 8, 0, 0, packet_id, packet_seq)
                chksum = checksum(header + data)
                header = struct.pack("bbHHh", 8, 0, chksum, packet_id, packet_seq)
                packet = header + data

    except socket.gaierror as e:
        print(f"Address {host} not found: {e}")
    except socket.error as e:
        print(f"Error: {e}")

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python ping.py <host> [-t] [-c count] [-w timeout]")
        sys.exit(1)

    host = sys.argv[1]
    infinite = "-t" in sys.argv
    count_index = sys.argv.index("-c") if "-c" in sys.argv else -1
    count = int(sys.argv[count_index + 1]) if count_index > 0 else 4
    timeout_index = sys.argv.index("-w") if "-w" in sys.argv else -1
    timeout = int(sys.argv[timeout_index + 1]) if timeout_index > 0 else 2

    ping(host, count, timeout, infinite)

这个程序使用了Python的socket库进行网络通信，发送和接收ICMP报文进行Ping操作。其中，checksum函数用于计算校验和，ping函数实现了四次Ping和无限次Ping的功能，可以根据参数进行控制。程序支持在命令行中通过参数指定Ping的目标主机、Ping次数、超时时间等参数。