[lwip-users] tcp failing first connection request

[Craig Clark]

I am using the http server in lwip version 1.4 (which was the latest
version when I started), but if the system is left for a few minutes the
first web request times out.  If you then make another, it all works
fine until you leave it sit for a few minutes, and the next web request
will then fail.

Looking at the debug data, I don't seem to be receiving the ack (3rd
part of the handshake) until immediately after tcp_slowtmr removes the
pcb for being stuck in SYN-RCVD (as I said, if this is the second
request, this works fine)

I doubled the timeout for SYN-RCVD (TCP_SYN_RCVD_TIMEOUT) and I got the
exact same result.  I am presuming that the transmission of my SYN+ACK
is being delayed, but I don't know why.

I did try enable ARP_QUEUEING, but it didn't seem to have any effect

Any thoughts on what I could have set wrong?

Thanks
Craig