Question

This is what i have:

std::string GetBytesAsHEX(const char *arr, int arr_size)
{
    BYTE ch = 0x00;
    char pseudo[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    std::string ret_val;

    for (int i = 0; i < arr_size; i++)
    {
        ch = (BYTE) (arr[i] & 0xF0);
        ch = (BYTE) (ch >> 4);
        ch = (BYTE) (ch & 0x0F);
        ret_val += pseudo[(int)ch];
        ch = (BYTE) (arr[i] & 0x0F);
        ret_val += pseudo[(int)ch];
        ret_val += ' ';
    }

    return ret_val;
}

int __stdcall Hooked_send(SOCKET s, const char *buf, int len, int flags)
{
    h_send.PreHook();
    //--------------

    int ret_val = send(s, buf, len, flags);

    if (LogPackets)
    {
        FILE *fptr = fopen("packet_log_hex.txt", "a");
        char header[128] = { 0 };
        sprintf(header, "\nSENT %i bytes: ", ret_val);
        fwrite(header, strlen(header), sizeof(char), fptr);
        fwrite(GetBytesAsHEX(buf, ret_val).c_str(), ret_val, sizeof(char), fptr);

        fclose(fptr);

        fptr = fopen("packet_log.txt", "ab");
        fwrite(buf, ret_val, sizeof(char), fptr);
        fclose(fptr);
    }

    //---------------
    h_send.PostHook();

    return ret_val;
}

int __stdcall Hooked_recv(SOCKET s, char *buf, int len, int flags)
{
    h_recv.PreHook(); //restore original recv address

    int ret_val = recv(s, buf, len, flags);

    if (ret_val > 0 && LogPackets)
    {
        FILE *fptr = fopen("packet_log_hex.txt", "a");
        char header[128] = { 0 };
        sprintf(header, "\nRECV %i bytes: ", ret_val);
        fwrite(header, strlen(header), sizeof(char), fptr);
        fwrite(GetBytesAsHEX(buf, ret_val).c_str(), ret_val, sizeof(char), fptr);

        fclose(fptr);

        fptr = fopen("packet_log.txt", "ab");
        fwrite(buf, ret_val, sizeof(char), fptr);
        fclose(fptr);
    }

    h_recv.PostHook(); //replace recv address with Hooked_recv

    return ret_val;
}

and this is what i get in file packet_log_hex.txt

SENT 16 bytes: 55 47 0C 00 00 0 //this is way not 16 bytes... and why so weird termination?
RECV 32 bytes: 55 47 1C 00 00 00 10 00 03 00 00
RECV 16 bytes: 55 47 0C 00 00 0
SENT 16 bytes: 55 47 0C 00 00 0
RECV 16 bytes: 55 47 0C 00 00 0
SENT 16 bytes: 55 47 0C 00 0B 0
RECV 16 bytes: 55 47 0C 00 00 0
SENT 16 bytes: 55 47 0C 00 10 F
RECV 16 bytes: 55 47 0C 00 00 0
SENT 16 bytes: 55 47 0C 00 C5 E

packet_log.txt (this one contain pure bytes) (copied from hex editor)

55 47 0C 00 00 00 00 00 02 00 00 00 01 00 03 02
55 47 1C 00 00 00 10 00 03 00 00 00 2D 04 00 00 50 07 F3 17 1A 37 34 48 81 D2 5E 13 73 21 37 A3
55 47 0C 00 00 00 00 00 12 00 00 00 00 00 00 00
55 47 0C 00 00 00 00 00 12 00 00 00 30 00 00 00
55 47 0C 00 00 00 00 00 12 00 00 00 00 00 00 00
55 47 0C 00 0B 00 00 00 12 00 00 00 40 00 00 00
55 47 0C 00 00 00 00 00 12 00 00 00 00 00 00 00
55 47 0C 00 10 FB 00 00 12 00 00 00 50 00 00 00
55 47 0C 00 00 00 00 00 12 00 00 00 00 00 00 00
55 47 0C 00 C5 EE 00 00 12 00 00 00 60 00 00 00

uhh, you see that.

Answer 1

The ret_val you are using in the following line:

fwrite(GetBytesAsHEX(buf, ret_val).c_str(), ret_val, sizeof(char), fptr);

is the number of bytes you have received from the recv() call. This is not the number of bytes you need to write to the file after you have converted the received bytes to a hex string separated by spaces. Your call should probably be:

std::string hex_str = GetBytesAsHEX(buf, ret_val);
fwrite(hex_str.c_str(), hex_str.length(), sizeof(char), fptr);

As for the weird termination, this is caused by the same thing. You can see that you are writing exactly 16 bytes in the first line by simply counting them, but it is 16 bytes of the converted string:

          111111
0123456789012345

55 47 0C 00 00 0