recv（）在非阻塞tcp ip套接字的对等端断开时返回-1

Question

我正在使用TCP/IP套接字，我已经读过recv函数。因此，每当对等体断开连接时，recv按照文档返回0，但在windows上它不返回零，而是返回-1，并且errono中的值是0我无法理解它为什么这样做。同样的代码在Linux中运行得非常好。

// some headers i used
#ifdef _WIN32
/* See http://stackoverflow.com/questions/12765743/getaddrinfo-on-win32 */
#    ifndef _WIN32_WINNT
#        define _WIN32_WINNT 0x0501 /* Windows XP. */
#    endif
#    include <Ws2tcpip.h>
#    include <winsock2.h>

#    ifdef _MSC_VER
#        pragma comment(lib, "Ws2_32.lib")
#    endif

#    define SHUT_RDWR SD_BOTH
#else
/* Assume that any non-Windows platform uses POSIX-style sockets instead. */
#    include <arpa/inet.h>
#    include <fcntl.h>
#    include <netinet/in.h>
#    include <netinet/tcp.h>
#    include <sys/socket.h>
#    include <unistd.h>

#    define NO_ERROR 0
#    define INVALID_SOCKET -1
#    define SOCKET_ERROR -1
#endif

// MSG_DONTWAIT is not available on some platforms, if it doesn't exist define it as 0
#if !defined(MSG_DONTWAIT)
#    define MSG_DONTWAIT 0
#endif
//

std::vector<std::string> Peer::read(const int length)
{
    static std::vector<char> tempRecvBuf(2 * 1000000);
    tempRecvBuf.clear();
    int recv = ::recv(m_socket.resource(), &tempRecvBuf[0], length, MSG_DONTWAIT);

    if (recv == SOCKET_ERROR ) {
        if (errno == WSAECONNRESET) {
            return {};
        }
        else {
            return {};
    }

    if (recv == 0) {
        // Connection is no longer valid, remote has been disconnected
        m_connected = false;
        this->m_master->events()->onPeerDisconnect()->trigger(this);
        this->m_master->peers()->remove(this);
        return {};
    }

Answer 1

根据Microsoft Windows套接字文档的这一页，函数recv将在正常关闭时返回0；在错误（包括中止关闭）时返回socket_error（可能定义为-1)。如文档中所述，您必须调用WSAGETLastError来获取错误代码。它不存储在errno中。