Thanks for your reply. I think I already understood this, though it
probably wasn't clear from the code fragment I posted. In my code,
iClientSock was the result of an accept().
I should have posted something more like;
FD_ZERO(&readset);
FD_SET(iServerSock, &readset);
iNumSocks = iServerSock + 1;
if ( iClientSock >= 0 )
{
FD_SET(iClientSock, &readset);
if ( iClientSock + 1 > iNumSocks )
iNumSocks = iClientSock + 1;
}
selectTimeout.tv_sec = 0;
selectTimeout.tv_usec = POLL_TIMEOUT * 1000;
if ( lwip_select(iNumSocks, &readset, NULL, NULL, &selectTimeout) == 0
)
return 0;
if ( iClientSock >= 0 && ( FD_ISSET(iClientSock, &readset) ) )
{
/* Do a read .... */
}
else if ( FD_ISSET(iServerSock, &readset) )
{
/* Server socket readable, we have a new connection request */
tAddrlen = sizeof(tAddr);
iClientSock = lwip_accept(iServerSock, (struct sockaddr *) &tAddr,
&tAddrlen);
The fragment is called periodically, with the iServerSock already in the
listen state, and iClientSock == -1.
On Thu, May 29, 2008 at 3:48 PM, Muhamad Ikhwan Ismail <
[EMAIL PROTECTED]> wrote:
>
> Hi,
>
> Once a client socket has been accepted, lwip_select always returns 1. I
> then test the client socket with
>
> if ( iClientSock >= 0 && FD_ISSET(iClientSock, &readset) )
>
> Which is always true (after the client socket has been accepted).
>
> I can read data once it has been sent, and send on the socket. The
> SO_RCVTIMEO option doesn't seem to change this behaviour. I've tried lwip
> 1.3.0, and the version from cvs today. I'm using FreeRTOS on a small ARM
> chip, the atmel AT91SAM7X256.
>
> When a connection is accepted, you get a new socket with which you execute
> the I/O operations. You do not do I/O with the same socket used to
> established connection
> which I see you are doing. Which is why you always get one when you used
> select with the iClientSocket. This is standard for all socket API.
>
> You should have during the accept (after select returns 1 for accetpt) :
>
> int iQClientSock = accept(....);
>
> and for future I/O operration used the iQClientSocket :
>
> if ( iQClientSock >= 0 && FD_ISSET(iQClientSock, &readset) )
>
> I hope I understood your questions and my answer could help you.
>
> Greetings
> Ikhwan
>
>
>
> ------------------------------
> Date: Thu, 29 May 2008 15:21:08 +0800
> From: [EMAIL PROTECTED]
> To: [email protected]
> Subject: [lwip-users] TCP server app, using select
>
>
> Hi
>
> I'm having a problem using select() in my TCP server application, and I
> hope someone can point out where I'm mistaken. It seems to always mark my
> accepted client sockets as readable, even when there is no data to be read.
>
> I'd like my task to:
> - periodically service some of my own functions,
> - accept incoming tcp connections and
> - service any already received connection.
> It should drop current connections in favour of new connections if the old
> connection doesn't have any data.
>
> I've designed my code to first do a select on the server socket after the
> bind() and a listen(). The select has a timeout.
>
> Once the server socket is readable, I do an lwip_accept() to get the client
> socket number. I then use the SO_RCVTIMEO socket option to set the read
> timeout for the socket.
>
> I try a lwip_recvfrom() on the client socket, which returns 0.
>
> If I then call lwip_select() with both the server and client sockets in the
> readset, it will always return the readset with the client socket marked. A
> subsequent recv of the client socket returns 0, unless there actually is
> data to read.
>
> I can't follow the lwip_select() code entirely, but it seems that the
> problem may be in the accept. There is a line;
>
> nsock->rcvevent += -1 - newconn->socket;
>
> This affects the subsequent select, which tests the socket with
>
> if (p_sock && (p_sock->lastdata || p_sock->rcvevent))
>
>
> My call to select is as follows;
>
> FD_ZERO(&readset);
> FD_SET(iServerSock, &readset);
> iNumSocks = iServerSock + 1;
> if ( iClientSock >= 0 )
> {
> FD_SET(iClientSock, &readset);
> if ( iClientSock + 1 > iNumSocks )
> iNumSocks = iClientSock + 1;
> }
>
> selectTimeout.tv_sec = 0;
> selectTimeout.tv_usec = POLL_TIMEOUT * 1000;
>
> if ( lwip_select(iNumSocks, &readset, NULL, NULL, &selectTimeout) ==
> 0 )
> return 0;
>
> Once a client socket has been accepted, lwip_select always returns 1. I
> then test the client socket with
>
> if ( iClientSock >= 0 && FD_ISSET(iClientSock, &readset) )
>
> Which is always true (after the client socket has been accepted).
>
> I can read data once it has been sent, and send on the socket. The
> SO_RCVTIMEO option doesn't seem to change this behaviour. I've tried lwip
> 1.3.0, and the version from cvs today. I'm using FreeRTOS on a small ARM
> chip, the atmel AT91SAM7X256.
>
>
> Thanks in advance
>
>
>
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