select() waiting for timeout before doing anything

Hi,

I've written a tcp/ip client in C. For all reading I use select() The
idea behind this is, that the client has threads which can't read from
the socket all at one time, so a thread with the select call is
"instructing" other threads. When something is written from the server,
the client waits until the timeout of the select has been reached before
doing anything. There's only 1 FD is de fd_set and that's the socket.
Doesn't select "respond" when something is tried to be written on a fd?

Thanks in advanced,

Frank de Bot!

Frank de Bot <ppi_doenst@like_spam.searchy.net> wrote:
> I've written a tcp/ip client in C. For all reading I use select() The
> idea behind this is, that the client has threads which can't read from
> the socket all at one time, so a thread with the select call is
> "instructing" other threads. When something is written from the server,
> the client waits until the timeout of the select has been reached before
> doing anything. There's only 1 FD is de fd_set and that's the socket.
> Doesn't select "respond" when something is tried to be written on a fd?

Yes. Therefore your code is wrong.

(lacking telepathy and vision-at-a-distance of course I cannot tell
what is wrong with it - I would guess the fd+1 count is not fd+1,
but 1)

Peter

I've ran the process with strace and de fd_set is losing fd's :-S

[pid 9827] select(9, [0 8], NULL, NULL, {2, 500000}) = 1 (in [8], left
{2, 500000})
[pid 9827] select(9, [8], NULL, NULL, {2, 500000} <unfinished ...>

Could this be any clue what's wrong?

Frank


Peter T. Breuer wrote:
> Frank de Bot <ppi_doenst@like_spam.searchy.net> wrote:
>
>>I've written a tcp/ip client in C. For all reading I use select() The
>>idea behind this is, that the client has threads which can't read from
>>the socket all at one time, so a thread with the select call is
>>"instructing" other threads. When something is written from the server,
>>the client waits until the timeout of the select has been reached before
>>doing anything. There's only 1 FD is de fd_set and that's the socket.
>>Doesn't select "respond" when something is tried to be written on a fd?
>
>
> Yes. Therefore your code is wrong.
>
> (lacking telepathy and vision-at-a-distance of course I cannot tell
> what is wrong with it - I would guess the fd+1 count is not fd+1,
> but 1)
>
> Peter

Frank de Bot <ppi_doenst@like_spam.searchy.net> writes:

> I've ran the process with strace and de fd_set is losing fd's :-S
>
> [pid 9827] select(9, [0 8], NULL, NULL, {2, 500000}) = 1 (in [8], left
> {2, 500000})
> [pid 9827] select(9, [8], NULL, NULL, {2, 500000} <unfinished ...>
>
> Could this be any clue what's wrong?

Are you initializing the descriptor set before each call to select()?
Neglecting to do so is a common mistake.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/