c - Ubuntu 中的 FTP 主动模式客户端错误 : I won't open a connection to 127. 0.1.1

Question

我已经创建了 FTP 主动模式客户端。在 OS X 操作系统上它运行得很好。但是当我迁移到 Ubuntu 时，它开始失败。问题是，在 OS X 上，当我启用数据连接时，我的监听套接字会监听我的 wifi 路由器 IP。我不知道为什么，但在我的 Ubuntu 上它监听 127.0.1.1。因此，我得到了对 PORT 命令的响应:

I won't open a connection to 127.0.1.1

如何像在 OS X 中一样确定主机的优先级？

数据连接:

    else if (strcmp(command, "ls") == 0)
    {
        // Listening data socket initialization
        data_socket = listen_to_server(&ip_address);

        if (data_socket == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // FTP commad PORT request
        if(request_port(&command_socket, ip_address) == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // Server response receiving
        if(receive_packet(&command_socket, packet) == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // Server response printing
        printf ("%s\n", packet);

        // FTP command LIST request
        if(request_list(&command_socket) == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // Server response receiving
        if(receive_packet(&command_socket, packet) == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // Server response printing
        printf ("%s\n", packet);

        // Server connection accepting (Active mode)
        int address_size = sizeof(struct sockaddr_in);
        struct sockaddr_in remote_address;

        data_socket_server = accept(data_socket, (struct sockaddr *)&remote_address, (socklen_t *)&address_size);

        // Server response receiving
        if(receive_packet(&command_socket, packet) == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // Server response printing
        printf ("%s\n", packet);

        // Server data receiving
        if(receive_packet(&data_socket_server, packet) == SOCKET_ERROR)
        {
            goto EXIT;
        }

        // Server data printing
        printf ("%s\n", packet);

        // Sockets closing
        closesocket(data_socket_server);
        closesocket(data_socket);
    }

监听套接字创建:

// Listening to server function
SOCKET listen_to_server(char **ip)
{
    // SOCKET variable
    SOCKET data_socket;
    // SOCKET address structure
    struct sockaddr_in socket_address;
    // Listening host name
    char host_name [256] = {0};
    // Listening host entry
    struct hostent *host_entry;

    // Host name initialization
    if (gethostname(host_name, sizeof(host_name)) == INVALID_SOCKET)
    {
        printf("Error: failed to get host  name\n");

        return INVALID_SOCKET;
    }

    // Host entry structure initialization
    if ((host_entry = gethostbyname(host_name)) == NULL)
    {
        printf("Error: failed to get host by name \'%s\'\n", host_name);

        return INVALID_SOCKET;
    }

    // Socket address structure initialization
    socket_address.sin_family = AF_INET;
    socket_address.sin_port = htons(DATA_PORT);
    socket_address.sin_addr = *(struct in_addr *)host_entry -> h_addr;
    memset (&(socket_address.sin_zero), 0, 8);

    // Socket initialization
    if ((data_socket = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
    {
        printf("Error: failed to initialize socket\n");

        return INVALID_SOCKET; 
    }

    // Socket and address binding
    if (SOCKET_ERROR == bind(data_socket, (struct sockaddr *)&socket_address,    sizeof(socket_address)))
    {
        printf("Error: failed to bind socket\n");

        closesocket(data_socket);

        return INVALID_SOCKET;
    }

    // Socket seting as listening
    if (SOCKET_ERROR == listen(data_socket, MAX_QUEUE_LENGTH))
    {
        printf("Error: failed to set socket as listening\n");

        closesocket (data_socket);

        return INVALID_SOCKET;
    }

    *ip = inet_ntoa(*(struct in_addr *)host_entry -> h_addr);

    return data_socket;
}

另外，netstat 不显示监听数据 soxket 外部地址:

tcp        0      0 127.0.1.1:1024          0.0.0.0:*               LISTEN

Answer 1

if ((host_entry = gethostbyname(host_name)) == NULL)
...
socket_address.sin_addr = *(struct in_addr *)host_entry -> h_addr;
...
if (SOCKET_ERROR == bind(data_socket, (struct sockaddr *)&socket_address,    sizeof(socket_address)))

看起来您只是假设系统本地配置的主机名将解析为外部地址。这个假设是错误的。

您应该使用 FTP 控制连接的本地地址 (getsockname) 作为数据连接的本地地址。