3. 编写代码实现TCP的活跃主机发现，要求探测的目标主机实现固定和手工输入（单个或区间主机）和实现区间主机自动化TCP探测，共编写三种

编写TCP活跃主机发现的代码通常涉及网络编程和多线程技术。这里提供一个简化版的概念和伪代码示例，实际实现可能会更复杂，依赖于特定的编程语言如Python、Java等：

1. **固定IP探测** (Single IP)

import socket

def check_host(ip):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(5)  # 设置超时时间
    try:
        response = sock.connect_ex((ip, 80))  # 连接HTTP端口，成功返回0
        if response == 0:
            print(f"{ip} is alive")
        else:
            print(f"{ip} is not responding")
    finally:
        sock.close()

# 调用函数并传入目标IP
check_host("192.168.1.1")

2. **手动输入IP范围探测** (Interval of IPs)

start_ip, end_ip = input("Enter start and end IP range (e.g., 192.168.1.1-10): ").split("-")

for ip in range(int(start_ip), int(end_ip)+1):
    check_host(ip)

3. **自动化的IP区间探测** (Range with loop)

from itertools import count

def scan_range(start_ip, end_ip):
    for i in count(start_ip, 1):
        if i > end_ip:
            break
        check_host(i)

scan_range("192.168.1.1", "192.168.1.254")  # 根据需要调整范围