非阻塞recv（）上的奇怪win sock错误

Question

这是我的非重叠套接字的接收文件函数。

            HANDLE recvfile = CreateFile(fileinfo[0], FILE_APPEND_DATA, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
            if (recvfile == INVALID_HANDLE_VALUE) {
                sockprintf(sockfd, "[Error Creating File] : %ld", GetLastError());
            }
            else {
                memset(recvbuf, '\0', BUFFER); // Clear main buffer
                int total = 0; // Total bytes received
                // set_blocking_mode(sockfd, FALSE);
                do{ // IF Total is equal to expected bytes. Break the loop, And stop receiving.
                    fsize = recv(sockfd, recvbuf, BUFFER, 0); // Receive file
                    if (fsize == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET)
                    {
                        connected = FALSE;
                        printf("[X] Connection interrupted while receiving file %s for %s size.", fileinfo[0], fileinfo[1]);
                    }
                    write = WriteFile(recvfile, recvbuf, fsize, &dwBytesWritten, NULL); // Write file data to file
                    total += fsize; // Add number of bytes received to total.
                } while(total != expected);
                // set_blocking_mode(sockfd, TRUE);
                if (write == FALSE)
                {
                    sockprintf(sockfd, "[Error Writing file %s of %s size] Error : %ld.", fileinfo[0], fileinfo[1], GetLastError());
                }
                else {
                    sockprintf(sockfd, "\n[ Received File : %s ]\n[ File Size : %s bytes ]\n[ Bytes written : %ld ]\n", fileinfo[0], fileinfo[1], dwBytesWritten);
                }
                CloseHandle(recvfile);
            }

这很好用！文件传输几乎是即时的，没有错误或损坏的缓冲区。 我在 Visual Studio 2019 上。问题是，当我编译可执行文件并将其移动到测试虚拟机时。程序崩溃。在 Windows 10 和 Windows 7 上测试。

在 do while 循环中发生崩溃。该程序不会摆脱它。我尝试使用 msvc（最新）以及 mingw-w64 和 tdm gcc 进行编译。错误是一样的。 该代码仅适用于我自己的机器，它不适用于任何其他机器。

Answer 1

您需要检查的不仅仅是 WSAECONNRESET。几乎每个错误（非阻塞中的“将阻塞”除外）都是致命的，并表明应该中止套接字。不要忘记，如果远程端优雅地结束，recv 可以并且将返回 0。

整个循环：

            do{ // IF Total is equal to expected bytes. Break the loop, And stop receiving.
                fsize = recv(sockfd, recvbuf, BUFFER, 0); // Receive file
                if (fsize == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET)
                {
                    connected = FALSE;
                    printf("[X] Connection interrupted while receiving file %s for %s size.", fileinfo[0], fileinfo[1]);
                }
                write = WriteFile(recvfile, recvbuf, fsize, &dwBytesWritten, NULL); // Write file data to file
                total += fsize; // Add number of bytes received to total.
            } while(total != expected);

应该是：

            do{ 
                fsize = recv(sockfd, recvbuf, BUFFER, 0); // Receive file
                if (fsize == SOCKET_ERROR) {

                    int err = WSAGetLastError();
                    if (err == WSAEWOULDBLOCK) {

                        // ISSUE SELECT CALL HERE TO WAIT FOR MORE DATA

                    }
                    else {
                        // FATAL ERROR - abort
                        break;
                    }

                }
                else if (fsize == 0) {
                    break;  // remote connection terminated cleanly.
                }
                else {
                    write = WriteFile(recvfile, recvbuf, fsize, &dwBytesWritten, NULL);
                    total += fsize;
                }
            } while(total != expected);

Answer 2

我已经解决了这个问题，看来问题是我自己的无知，服务器端提供文件信息的速度太快了，因此，fileinfo[] 混淆了。因此循环不会中断。仍然不明白为什么它在开发机器上工作。无论如何，正如预期的那样，问题不在我在此问题中发布的代码中。谢谢你们！ 解决方案是在睡眠时间较短的情况下发送数据。 :)