Re: Socket Buffering question

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

I would assume that this is a bug in your program...  If you're not 
sure, I'd try sniffing the connection to verify that the duplicated data 
isn't really being sent over the network.

However, I can't see anything in the part of the code you posted that 
would cause this -- then again, the part of the code you posted seems to 
be checking the output of select(), and NOT where you read the data from 
the socket, and tells nothing about how you're buffering it, so I would 
look in other areas of your code, if I were you.

in particular, make sure that when you read data from the read buffer 
for the socket (I'm assuming you maintain a read buffer for each socket 
in the MODS) you have to make sure that you remove the data you've read, 
and never ever read it again.


GKern@xxxxxxxxxxxxxxxx wrote:
> Repost from accidental post to Midrange-L:
>
> I'm using Scott Klement's socket tutorial as the template for a socket 
> server that uses non-blocking sockets with select() to support multiple 
> (3) clients at once.
>
> Right now I have only one client active, but for some reason when I 
> receive data, I receive the same data string x number of times over a 
> short period of minutes and in one instance over a period of about 50 
> minutes. 
>
> For example one message was received 23 times (in a row) and the next one 
> 27 times. 
> Following that the next five unique messages were received 27, 30, 14, 27 
> & 26 times (each received x number of times in a row).
>
> The client says they are not responsible for sending the same data 
> repeatedly.
>
> I'm wondering if the following code inserted into this subroutine in the 
> template to read & write to the buffers is incorrect and responsible for 
> this problem.
>
> Is this not the correct location (note code prefixed with gpk) to be 
> reading the input buffers and writing the output buffers? 
>
> sk   CSR   CheckSockets  begsr 
> sk   C*------------------------ 
> sk   c                   do        MAXCLIENTS    C 
> sk 
> sk   c     C             occur     client 
> sk 
> sk   c                   if        sock <> -1 
> sk 
> sk   c                   if        FD_ISSET(sock: readset) 
> sk   c                   if        ReadClient(C) < 0 
> sk   c                   callp     EndClient(C) 
> sk   c                   callp     FD_CLR(sock: excpset) 
> sk   c                   callp     FD_CLR(sock: writeset) 
> gpk   * Load socket data from input buffer, do custom processing, 
> gpk   *  and load the ACK to the output buffer... 
> gpk  C                   Else 
> gpk  C                   Eval      IscketData = *Blanks
> gpk  C                   Eval      IscketData = rdbuf  
> gpk  C                   Exsr      ReadIscket 
> gpk  C                   Eval      wrbuflen = %Len(OscketData) 
> gpk  C                   Eval      wrbuf = OscketData 
> sk   c                   endif 
> sk   c                   endif 
> sk 
> sk   c                   if        FD_ISSET(sock: writeset) 
> sk   c                   if        WriteClient(C) < 0 
> sk   c                   callp     EndClient(C) 
> sk   c                   callp     FD_CLR(sock: excpset) 
> sk   c                   callp     FD_CLR(sock: writeset) 
> sk   c                   endif 
> sk   c                   endif 
> sk 
> sk   c                   if        FD_ISSET(sock: excpset) 
> sk   c                   callp     EndClient(C) 
> sk   c                   endif 
> sk 
> sk   c                   endif 
> sk 
> sk   c                   enddo 
> sk   C*------------------------ 
> sk   CSR                 endsr