Windows – ConnectEx要求套接字“最初绑定”,但是要什么？

ConnectEx功能需要“未连接的,先前绑定的套接字”.实际上,如果我省略了我的示例中的 bind步骤(见下文),则 ConnectEx在 WSAEINVAL失败.

这是我目前的理解：在调用ConnectEx之前,bind将套接字调用到INADDR_ANY和端口0(除非它已被绑定)：

struct sockaddr_in addr;
ZeroMemory(&addr,sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = 0;
rc = bind(sock,(SOCKADDR*) &addr,sizeof(addr));
if (rc != 0) { ... bind Failed; call WSAGetLastError to see why ... }

或者对于IPv6套接字：

struct sockaddr_in6 addr;
ZeroMemory(&addr,sizeof(addr));
addr.sin6_family = AF_INET6;
addr.sin6_addr = in6addr_any;
addr.sin6_port = 0;
rc = bind(sock,sizeof(addr));
if (rc != 0) { ... bind Failed; call WSAGetLastError to see why ... }

这允许操作系统为我们的套接字分配本地地址(而不是我们连接的远程地址). connect自动执行此步骤,但ConnectEx不会.

我的问题是：

>我的评估是否正确？
>有没有办法对地址族进行无关的自动绑定,还是我必须手动处理AF_INET,AF_INET6,AF_BTH(蓝牙)等各个？

使用ConnectEx示例(也在Gist：https://gist.github.com/4158972上)：

#include <stdio.h>
#include <WinSock2.h>
#include <MSWSock.h>
#include <WS2tcpip.h>

#pragma comment(lib,"Ws2_32.lib")

struct mswsock_s {
    LPFN_CONNECTEX ConnectEx;
} mswsock;

static BOOL load_mswsock(void)
{
    SOCKET sock;
    DWORD dwBytes;
    int rc;

    /* Dummy socket needed for WSAIoctl */
    sock = socket(AF_INET,SOCK_STREAM,0);
    if (sock == INVALID_SOCKET)
        return FALSE;

    {
        GUID guid = WSAID_CONNECTEX;
        rc = WSAIoctl(sock,SIO_GET_EXTENSION_FUNCTION_POINTER,&guid,sizeof(guid),&mswsock.ConnectEx,sizeof(mswsock.ConnectEx),&dwBytes,NULL,NULL);
        if (rc != 0)
            return FALSE;
    }

    rc = closesocket(sock);
    if (rc != 0)
        return FALSE;

    return TRUE;
}

int main(int argc,char *argv[])
{
    int rc;
    BOOL ok;
    WSADATA wsaData;
    SOCKET sock;

    rc = WSAStartup(MAKEWORD(2,2),&wsaData);
    if (rc != 0) {
        printf("WSAStartup Failed: %d\n",rc);
        return 1;
    }
    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
        printf("Your computer is from the wrong millenium.\n");
        WSACleanup();
        return 1;
    }

    if (!load_mswsock()) {
        printf("Error loading mswsock functions: %d\n",WSAGetLastError());
        return 1;
    }

    sock = socket(AF_INET,0);
    if (sock == INVALID_SOCKET) {
        printf("socket: %d\n",WSAGetLastError());
        return 1;
    }

    /* ConnectEx requires the socket to be initially bound. */
    {
        struct sockaddr_in addr;
        ZeroMemory(&addr,sizeof(addr));
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = INADDR_ANY;
        addr.sin_port = 0;
        rc = bind(sock,sizeof(addr));
        if (rc != 0) {
            printf("bind Failed: %d\n",WSAGetLastError());
            return 1;
        }
    }

    /* Issue ConnectEx and wait for the operation to complete. */
    {
        OVERLAPPED ol;
        ZeroMemory(&ol,sizeof(ol));

        sockaddr_in addr;
        ZeroMemory(&addr,sizeof(addr));
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = inet_addr("173.194.37.36"); // google.com
        addr.sin_port = htons(80);

        ok = mswsock.ConnectEx(sock,sizeof(addr),&ol);
        if (ok) {
            printf("ConnectEx succeeded immediately\n");
        } else if (WSAGetLastError() == ERROR_IO_PENDING) {
            printf("ConnectEx pending\n");

            DWORD numBytes;
            ok = GetoverlappedResult((HANDLE) sock,&ol,&numBytes,TRUE);
            if (ok)
                printf("ConnectEx succeeded\n");
            else
                printf("ConnectEx Failed: %d\n",WSAGetLastError());
        } else {
            printf("ConnectEx Failed: %d\n",WSAGetLastError());
            return 1;
        }
    }

    /* Make the socket more well-behaved. */
    rc = setsockopt(sock,SOL_SOCKET,SO_UPDATE_CONNECT_CONTEXT,0);
    if (rc != 0) {
        printf("SO_UPDATE_CONNECT_CONTEXT Failed: %d\n",WSAGetLastError());
        return 1;
    }

    /* This will fail if SO_UPDATE_CONNECT_CONTEXT was not performed. */
    rc = shutdown(sock,SD_BOTH);
    if (rc != 0) {
        printf("shutdown Failed: %d\n",WSAGetLastError());
        return 1;
    }

    printf("Done\n");
    return 0;
}

connect does this step automatically,but ConnectEx does not.

正确.

Is my assessment correct?

是.

Is there a way to do this automatic bind that is agnostic to the address family,or will I have to handle each of AF_INET,AF_BTH (Bluetooth),etc. manually?

我相信INADDR_ANY在所有地址族中都是一堆零,所以你可以尝试使用memset()并完全省略addr.sin_addr.s_addr的赋值.这是否是犹太人,便携式,政治上正确等等,是我不会进入的另一个问题.

似乎很奇怪微软没有设法让ConnectEx()在内部调用bind(),考虑到保存系统调用是其存在的动机,并且还考虑到大多数程序根本不会绑定出站套接字.