c - 通过监控连接持续时间进行莫尔斯敲击

Question

最近了解了Port Knocking的概念。可以使用跟踪打开和关闭客户端连接的持续时间而不是打开端口吗？例如，发送 SOS（…………）

• 打开 3 个连接 100 毫秒：...
• 打开 3 个连接 300 毫秒：---
• 打开 3 个连接 100 毫秒：...

MSVC 示例

// Morse Knocking - Connection Duration: 100ms = dot, 300ms = dash.

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>

#pragma comment (lib, "Ws2_32.lib")
#pragma warning(disable : 4996)

#define dot 100
#define dash 300

int __cdecl main(int argc, char** argv)
{
    SOCKET client_socket;
    const int SIZE = 3;

    // Morse code distress signal ...---...
    char morse[SIZE] = { 'S', 'O', 'S'};

    WSADATA wsaData;

    WSAStartup(MAKEWORD(2, 2), &wsaData);

    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(80);
    server.sin_addr.s_addr = inet_addr("127.0.0.1");

    for (int i = 0; i < SIZE; i++)
    {
        switch (morse[i])
        {
        case 'S':
            for (int j = 0; i < 3; j++)
            {
                client_socket = socket(AF_INET, SOCK_STREAM, 0);
                connect(client_socket, (struct sockaddr*)&server, sizeof server);
                Sleep(dot);
                closesocket(client_socket);               
            }
        case 'O':
            for (int j = 0; j < 3; j++)
            {
                client_socket = socket(AF_INET, SOCK_STREAM, 0);
                connect(client_socket, (struct sockaddr*)&server, sizeof server);
                Sleep(dash);
                closesocket(client_socket);
            }
        default:
            exit(0);
        }
    }

    return 0;
}