端口扫描器开发问题：get_port函数返回None值求助

问题描述 #

开发端口扫描器时，get_port函数始终返回None，调试发现执行完port_is_valid函数后直接跳转到代码末尾，无法进入后续的端口处理逻辑。

原代码 #

import re
import termcolor


port_regex = re.compile(r'^\d{1,5}$|^\d{1,5}-\d{1,5}|\d{1,5}(,\d{1,5})*$')
def port_is_valid(port):
       result = bool(port_regex.match(port))
       print(result)


def get_port():
    str_ports = input(termcolor.colored("Specify The Ports: ", "light_cyan"))
    print(str_ports)

    if port_is_valid(str_ports):
        if "," in str_ports:
            nm_ports = str_ports.split(",")
            int_ports = [int(port) for port in nm_ports]
            print("sp")
            return int_ports
        elif "-" in str_ports:
            f_ports = []
            nm_ports = str_ports.split("-")
            if int(nm_ports[0]) > int(nm_ports[1]):
                print(termcolor.colored("order of ports range is not correct !!!", "red"))
                get_port()
                return None
            else:
                for port in range(int(nm_ports[0]), int(nm_ports[1]) + 1):
                    f_ports.append(port)
                print("rg")
                return f_ports
        else:
            try:
                int_port = int(str_ports)
                return int_port  
            except ValueError:
                print("Invalid port format")
                return None  # Return None for invalid single port


port_t = get_port()

问题原因 #

1. port_is_valid函数无返回值：该函数仅计算了验证结果并打印，但没有通过return返回结果，导致调用port_is_valid(str_ports)时永远得到None，if条件不成立，直接跳过所有端口处理分支，函数最终返回默认的None。
2. 递归调用结果被丢弃：当端口范围顺序错误时，递归调用get_port()后直接return None，新调用返回的有效端口列表被丢弃，仍然返回None。

修复后的代码 #

import re
import termcolor


port_regex = re.compile(r'^\d{1,5}$|^\d{1,5}-\d{1,5}|\d{1,5}(,\d{1,5})*$')
def port_is_valid(port):
       result = bool(port_regex.match(port))
       print(result)
       return result  # 添加返回语句


def get_port():
    str_ports = input(termcolor.colored("Specify The Ports: ", "light_cyan"))
    print(str_ports)

    if port_is_valid(str_ports):
        if "," in str_ports:
            nm_ports = str_ports.split(",")
            int_ports = [int(port) for port in nm_ports]
            print("sp")
            return int_ports
        elif "-" in str_ports:
            f_ports = []
            nm_ports = str_ports.split("-")
            if int(nm_ports[0]) > int(nm_ports[1]):
                print(termcolor.colored("order of ports range is not correct !!!", "red"))
                return get_port()  # 返回递归调用的结果，而非None
            else:
                for port in range(int(nm_ports[0]), int(nm_ports[1]) + 1):
                    f_ports.append(port)
                print("rg")
                return f_ports
        else:
            try:
                int_port = int(str_ports)
                return int_port  
            except ValueError:
                print("Invalid port format")
                return None  # 单端口格式错误时返回None


port_t = get_port()

内容的提问来源于stack exchange，提问作者ali eltaib