美好的一天!

我是一个在高级语言方面有一定经验的程序员，但这是我第一次深入研究低级语言的套接字代码，所以请多多包涵。

我似乎在调用 connect() 时出错。在我的主要函数中，WSAGetLastError() 打印出这是错误号 6，根据 MSDN 是 WSA_INVALID_HANDLE。这看起来很奇怪，因为在 MSDN page for the connect() function 上没有详细说明该特定错误代码。 (除非我要失明)，而且我的谷歌搜索都没有结果

我使用的是自定义 socket_t 结构，因为我的代码旨在(最终)跨平台。 socket_connect() 函数从主代码页调用。

socket_t 定义:

typedef struct
{
    //windows-specific
    SOCKADDR_IN *addr_in;
    u_long mode;
    SOCKET socket;//acutal SOCKET structure

    // General
    bool listening;//set to true if actively listening
    bool thread_terminate;//when boolean is set to true, listening thread terminates
    void (*error_callback) (int);
    http_response_t * response;
} socket_t;

socket_connect() 函数:

//see socket_t definition in socket.h
//returns 0 on success, SOCKET_ERROR on WinSock failure, positive error code on ANSI DNS failure
int socket_connect(socket_t * sock, char * addr, int port)
{
    //bear in mind sock is the custom socket_t structure.  sock->socket is the actual SOCKET structure.
    //pardon the nomenclature.  rookie code.

    //DNS lookup structures
    struct addrinfo     * res           = NULL;// Result of the getaddrinfo() call
    struct sockaddr_in  * sockaddr_v4   = NULL;// IPv4 sockaddr structure

    // So-called "hints" structure detailed in the getaddrinfo() MSDN page.
    // I guess it contains information for the DNS lookup.
    struct addrinfo hints;
    memset(&hints, 0, sizeof(hints));
    hints.ai_family     = AF_UNSPEC;
    hints.ai_socktype   = SOCK_STREAM;
    hints.ai_protocol   = IPPROTO_TCP;

    //Perform DNS lookup
    DWORD getaddrinfo_res = getaddrinfo(addr, "80\0", &hints, &res);//hard-code Port number for now...
    if(getaddrinfo_res != 0) return getaddrinfo_res;//positive DNS error code

            //debug information
    std::cout << "DNS lookup responses:" << std::endl;
    //for each
    int i = 0;//counter
    for(struct addrinfo * ptr = res; ptr != NULL; ptr = ptr->ai_next)
    {
        std::cout << "Response number " << i + 1 << std::endl;
        std::cout << "Flags: " << ptr->ai_flags << std::endl;

        std::cout << "Family: ";
        switch(ptr->ai_family)
        {
        case AF_INET:
            sockaddr_v4 = (struct sockaddr_in *) ptr->ai_addr;//set current address
            sock->addr_in = sockaddr_v4;//set socket address

            std::cout << "AF_INET (IPv4)" << std::endl;
            std::cout << "Addr: " << inet_ntoa(sockaddr_v4->sin_addr) << std::endl;
            break;
        case AF_UNSPEC:
            std::cout << "UNSPECIFIED" << std::endl;
            break;
        default:
            std::cout << "UNKNOWN\t(" << ptr->ai_family << ")" << std::endl;
            break;
        }

        i++;
    }

    //initialize actual SOCKET
    sock->socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);// TCP/IP, stream-oriented, and TCP rather than UDP; respectively
    if(sock->socket == INVALID_SOCKET) return SOCKET_ERROR;

    //actual connection
    std::cout << WSAGetLastError() << std::endl;
    int connect_res = connect(sock->socket, (SOCKADDR *) sockaddr_v4, sizeof(sockaddr_v4));///have to convert SOCKADDR_IN to a SOCKADDR pointer here.  Not sure why.
    if(connect_res == SOCKET_ERROR) return SOCKET_ERROR;

    //make nonblocking
    /*
    sock->mode = 1;
    int ioctl = ioctlsocket(sock->socket, FIONBIO, &(sock->mode));//I/O Control Socket.  Not sure what FIONBIO means.  pointer to sock->mode = 1 ensures nonblockingness.
    if(ioctl == SOCKET_ERROR) return SOCKET_ERROR;
    */// (include this?)

    return 0;
}

socket_connect() 函数调用:

int connect_res = conley::socket_connect(sock, "www.google.com", 80);
if(connect_res > 0) std::cout << "DNS ERR " << connect_res << std::endl << std::endl;
if(connect_res < 0) std::cout << "CONNECT ERR " << WSAGetLastError() << std::endl << std::endl;
if(connect_res == 0) std::cout << "Connected" << std::endl << std::endl;

感谢您的宝贵时间! - jack

最佳答案

当您调用 connect 时，您为 sockaddr_in 传递了错误的大小。

改变这个:

int connect_res = connect(sock->socket, (SOCKADDR *) sockaddr_v4, sizeof(sockaddr_v4));
//                                                            wrong size ^^^^^^^^^^^

对此:

int connect_res = connect(sock->socket, (SOCKADDR *) sockaddr_v4, sizeof(*sockaddr_v4));
//                                                            right size  ^^^^^^^^^^^

除此之外，您的程序还有一个不同的错误，即 getaddrinfo() 的持久性 - 在您的 sock 结构中返回指针。这应该按值复制到 sock 拥有的内存中。它将与此示例一起使用，因为它是如此孤立，但应该对其进行更改。

关于C++ WinSock2 : WSA_INVALID_HANDLE on connect() call，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18814019/