[lwip-users] Re opening LWIP for new HTTP message

[H.A.]

I am using LWIP 1.3.2 and software based on the Stellaris ser2enet (Cortex
M3) example. It runs a web server  for configuration plus a simple http
client based on the telnet client. All dedicated telnet processing has been
removed so it is basically using raw data. Data comes in on a serial port
and is assembled in a global buffer in the serial receive interrupt routine
until complete. Data is than transmitted with tcp_write on port 80 to a
server and flushed out with tcp_output straight from the interrupt routine.
We can expect to have new data perhaps once per hour and it is normally
around 130 bytes.

It works but the server shuts down the connection every 10 seconds. LWIP
detects this and does a callback to telnet_error which tears down the old
connection completely (4 TCP messages) and reconnects (3 TCP messages). As
far as I can see these messages are all empty from a TCP point of view (they
manipulate the flags). And they are all 60 bytes.

We could perhaps have a couple of hundred of these devices connected to a
single server so I am a little bit worried about the unnecessary Ethernet
traffic, disconnect/connect, when there really is no new data available.

Have tried several things like opening a new connection inside the serial
receive routine instead from the error callback. Didn’t work. What is the
best way to solve this. Opening the connection from somewhere else? How?

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