WriteFile, ERROR_INVALID_PARAMETER

Question 1

Ok, i'found what was wrong, the analogy with serial com cannot be used, instead i used the winsock class :

http://msdn.microsoft.com/en-us/library/windows/desktop/ms738545(v=vs.85).aspx

===================================================================================================== initialisation :

WSADATA wsaData;

    int iResult;
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

// ======================================================================================================
// Création du Socket : 
    struct addrinfo *result = NULL,
                *ptr = NULL,
                hints;

    ZeroMemory( &hints, sizeof(hints) );
    hints.ai_family = AF_INET ;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    #define DEFAULT_PORT "27015"

    // Resolve the server address and port
    iResult = getaddrinfo("10.10.100.254","8899" , &hints, &result); //"10.10.100.254" DEFAULT_PORT  "8899"
    if (iResult == 0) {
        printf("\n\t\tgetaddrinfo, adresse trouvee\n");

        struct addrinfo *res = NULL;
        int error;
        for (res = result; res != NULL; res = res->ai_next)
        {
            char hostname[NI_MAXHOST] = "";

            error = getnameinfo(res->ai_addr, res->ai_addrlen, hostname, NI_MAXHOST, NULL, 0, 0);
            if (error != 0)
            {
                fprintf(stderr, "error in getnameinfo: %s\n", gai_strerror(error));
                continue;
            }
            if (*hostname != '\0')
            {
                printf("hostname: %s\n", hostname);
                ptr=res;
            }
        }
    }else
    {
        printf("getaddrinfo failed: %d\n", iResult);
        WSACleanup();
        return 1;
    }

    SOCKET ConnectSocket = INVALID_SOCKET;

    // Attempt to connect to the first address returned by
    // the call to getaddrinfo


    // Create a SOCKET for connecting to server
    ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);

    if (ConnectSocket == INVALID_SOCKET) {
        printf("Error at socket(): %ld\n", WSAGetLastError());
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

// ======================================================================================================
// Connect to a socket :
    iResult = connect( ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
    if (iResult == SOCKET_ERROR) {
        wprintf(L"socket function failed with error: %ld\n", WSAGetLastError());
        switch(WSAGetLastError())
        {
        case WSAEHOSTUNREACH:
            wprintf(L"\n\t\tNo route to host. A socket operation was attempted to an unreachable host. See WSAENETUNREACH.\n");
            break;
        default:
            break;
        }
        closesocket(ConnectSocket);
        ConnectSocket = INVALID_SOCKET;

    }

    // Should really try the next address returned by getaddrinfo
    // if the connect call failed
    // But for this simple example we just free the resources
    // returned by getaddrinfo and print an error message

    freeaddrinfo(result);

    if (ConnectSocket == INVALID_SOCKET) {
        printf("Unable to connect to server!\n");
        WSACleanup();
        return 1;
    }

// ======================================================================================================
// Send and recive data : 
    #define DEFAULT_BUFLEN 512

    int recvbuflen = DEFAULT_BUFLEN;

    char *sendbuf = "this is a test";
    //char recvbuf[DEFAULT_BUFLEN];

    // Send an initial buffer

    for(int i = 0; i<100;i++)
    {
        if(sendCommand(ConnectSocket,i, i, 0, i)==-1) break;
        Sleep(10);
    }

// Disconnecting the Client : http://msdn.microsoft.com/en-us/library/windows/desktop/bb530743(v=vs.85).aspx
// shutdown the send half of the connection since no more data will be sent
    iResult = shutdown(ConnectSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed: %d\n", WSAGetLastError());
        closesocket(ConnectSocket);
        WSACleanup();
        return 1;
    }

    // cleanup
    closesocket(ConnectSocket);
    WSACleanup();

this worked fin for me

Question 2

Your switch to Windows sockets looks good. The only suggestions I'd have is, if you need cross-version compatibility, adding some fallback logic incase WSAStartup fails finding 2.2 that you're requesting.

Other suggestions would be stylistic, mainly to clean up your usage of WSACleanup by consolidating cleanup code for all the cases - such as using an SEH/leave or a goto fail case.