Using htons() in my code puts all zeros in the buffer and I don't understand why-CodePudding

I need to use htons() in my code to convert the little-endian ordered short to a network (big-endian) byte order. I have this code:

int PacketInHandshake::serialize(SOCKET connectSocket, BYTE* outBuffer, ULONG outBufferLength) {
    memset(outBuffer, 0, outBufferLength);
    const int sizeOfShort = sizeof(u_short);
    u_short userNameLength = (u_short)strlen(userName);
    u_short osVersionLength = (u_short)strlen(osVersion);
    int dataLength = 1   (sizeOfShort * 2)   userNameLength   osVersionLength;
    outBuffer[0] = id;
    outBuffer[1] = htons(userNameLength);// htons() here
    printf("u_short byte 1: %c%c%c%c%c%c%c%c\n", BYTE_TO_BINARY(outBuffer[1]));
    printf("u_short byte 2: %c%c%c%c%c%c%c%c\n", BYTE_TO_BINARY(outBuffer[2]));
    for (int i = 0; i < userNameLength; i  ) {
        outBuffer[1   sizeOfShort   i] = userName[i];
    }
    outBuffer[1   sizeOfShort   userNameLength] = htons(osVersionLength);// and here
    for (int i = 0; i < osVersionLength; i  ) {
        outBuffer[1   (sizeOfShort * 2)   userNameLength   i] = osVersion[i];
    }
    int result;
    result = send(connectSocket, (char*)outBuffer, dataLength, 0);
    if (result == SOCKET_ERROR) {
        printf("send failed with error: %d\n", WSAGetLastError());
    }
    printf("PacketInHandshake sent: %ld bytes\n", result);
    return result;
}

Which results in a packet like this to be sent:

As you see, the length indication bytes where htons() is used are all zeros, where they should be 00 07 and 00 16 respectively.

And this is the console output:

u_short byte 1: 00000000
u_short byte 2: 00000000
PacketInHandshake sent: 34 bytes

If I remove the htons() and just put the u_shorts in the buffer as they are, everything is as expected, little-endian ordered:

u_short byte 1: 00000111
u_short byte 2: 00000000
PacketInHandshake sent: 34 bytes

So what am I doing wrong?

CodePudding user response：

htons converts integers. This is how I used to do this.

    *(int16_t *)(&outBuffer[1]) = htons(userNameLength);

Note that this won't work on all systems because of alignment. This wasn't a problem on any system where I used to write it, but it is on some modern systems (but not x86 or x64).

Now I write (casts suppress compiler warnings):

    outbuffer[1] = (unsigned char)(userNameLength >> 8);
    outbuffer[2] = (unsigned char)userNameLength;

I now use the second because there isn't an htonq. Alignment problems don't come up for me because I design my buffers around the problem, but you did not.