Weird win sock bug on non blocking recv() - c

Question

This is my receive file function for a non overlapped socket.
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);
}
This is working excellent! File Transfer is almost instant and with no errors or corrupted buffers.
I'm on Visual studio 2019. The Problem is, When I compile and move the Executable to a test Virtual machine. The program crashes. Tested on Windows 10 and also Windows 7.
Crash occurs on the do while loop. The program does not break out of it. I have tried compiling with msvc (the latest) and also mingw-w64 and also tdm gcc. The bug is same.
The code only works on my own machine, It's not working on any other.

Answer 1

You need to check for more than just WSAECONNRESET. Pretty much every error (save for "would block" in non-blocking) is fatal and indicates the socket should be aborted. Don't forget that recv can and will return 0 if the remote side closes its end gracefully.
This whole loop:
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);
Should be:
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

I have resolved the issue, IT seems the problem was my own ignorance, The server side was supplying the file information too quickly, And due to that, fileinfo[] was mixed up. And thus the loop not breaking. Still don't understand why it worked on the development machine tho. Anyway, As expected the problem was not in the Code that I have posted in this Question. Thanks ya'll!
The solution was to send the data with a small time sleep. :)