C ++关闭套接字以启动新连接

Question

我是 C++ 套接字编程的新手。 我制作了一个简单的端口扫描器，它扫描一个端口，它按预期工作。

现在我正在尝试扫描多个端口，因此我创建了一个套接字并开始迭代一组端口，但所有端口都显示为已关闭。

我的问题是：我必须关闭套接字才能扫描另一个端口吗？

代码如下：

    // This Code scan correctly
    // ------------------------
    for (int i = 0; i < 7; i++)
    {
        int sock_fd = socket(AF_INET, SOCK_STREAM, 0);

        struct timeval timeout;
        timeout.tv_sec = 0;
        timeout.tv_usec = 260000; //750000 = 0.75s

        if(setsockopt(sock_fd, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout, sizeof(timeout)) < 0)
            std::cout << "Cannot set RCV timeout\n";
        if(setsockopt(sock_fd, SOL_SOCKET, SO_SNDTIMEO, (char*)&timeout, sizeof(timeout)) < 0)
            std::cout << "Cannot set SND timeout\n";

        struct sockaddr_in srv_addr;
        srv_addr.sin_family = AF_INET;
        srv_addr.sin_port = htons(ports[i]);
        inet_pton(AF_INET, "192.168.100.1", &srv_addr.sin_addr.s_addr);

        int connection_result = connect(sock_fd, (struct sockaddr*)&srv_addr, sizeof(srv_addr));
        if(connection_result == 0)
        {
            std::cout << "Port Open\n";
            close(sock_fd);
        }
        else
        {
            std::cout << "Port closed\n";
            close(sock_fd);
        }
    }

但是这段代码我在for循环之外创建/关闭套接字显示所有端口都关闭了！

        // Shows all ports close
        // ----------------------
        int sock_fd = socket(AF_INET, SOCK_STREAM, 0);
        for (int i = 0; i < 7; i++)
        {
        //int sock_fd = socket(AF_INET, SOCK_STREAM, 0);

        struct timeval timeout;
        timeout.tv_sec = 0;
        timeout.tv_usec = 100000; //750000 = 0.75s
        if(setsockopt(sock_fd, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout, sizeof(timeout)) < 0)
            std::cout << "Cannot set RCV timeout\n";
        if(setsockopt(sock_fd, SOL_SOCKET, SO_SNDTIMEO, (char*)&timeout, sizeof(timeout)) < 0)
            std::cout << "Cannot set SND timeout\n";
        struct sockaddr_in srv_addr;
        srv_addr.sin_family = AF_INET;
        srv_addr.sin_port = htons(ports[i]);
        inet_pton(AF_INET, "192.168.100.1", &srv_addr.sin_addr.s_addr);
        int connection_result = connect(sock_fd, (struct sockaddr*)&srv_addr, sizeof(srv_addr));
        if(connection_result == 0)
        {
            std::cout << "Port Open\n";
            //close(sock_fd);
        }
        else
        {
            std::cout << "Port closed\n";
            //close(sock_fd);
        }

        }
        close(sock_fd);

Answer 1

显然我必须关闭每个连接之间的套接字，感谢一些程序员老兄

所以我更改了我的代码，现在我在 for 循环中创建/关闭套接字。

下面的例子：

        for (int i = 0; i < 7; i++)
        {
        // Creating the socket
        // -------------------
        int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);

        struct timeval timeout;
        timeout.tv_sec = 5;
        timeout.tv_usec = 260000; //260000 = 0.26s
        if(setsockopt(sock_fd, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout, sizeof(timeout)) < 0)
            std::cout << "Cannot set RCV timeout\n";
        if(setsockopt(sock_fd, SOL_SOCKET, SO_SNDTIMEO, (char*)&timeout, sizeof(timeout)) < 0)
            std::cout << "Cannot set SND timeout\n";
        struct sockaddr_in srv_addr;
        srv_addr.sin_family = AF_INET;
        srv_addr.sin_port = htons(ports[i]);
        inet_pton(AF_INET, "192.168.100.1", &srv_addr.sin_addr.s_addr);
        int connection_result = connect(sock_fd, (struct sockaddr*)&srv_addr, sizeof(srv_addr));
        if(connection_result == 0)
        {
            std::cout << "Port Open\n";
            // Closing the socket
            close(sock_fd);
        }
        else
        {
            std::cout << "Port closed\n";
            // Closing the socket
            close(sock_fd);
        }

        }