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Re: [lwip-users] netconn_write blocking

From: address@hidden
Subject: Re: [lwip-users] netconn_write blocking
Date: Tue, 09 Oct 2007 21:28:25 +0200
User-agent: Thunderbird (Windows/20070728)

I have an application that is sending out TCP data to several client using the sequential API. When a client disconnects gracefully, netconn_write returns a negative value, and I can close the connection. However, if any of the clients locks up (i'm using embedded clients), or a cable gets unplugged, etc. netconn_write keeps queue packets until it fills up the buffer, and then blocks. I've been playing around with debugging, and so far all I get is lots of messages about the queue being full.
It complains about the queue being full?? That would be a misconfiguration and maybe an error in your port! The queues should never be full! That's why sys_arch_mbox_post has no return value, and the port should assert to check that a queue is never full. Misconfiguration could lead to this: too big TCP windows vs. too small queues...

But to be sure about this, could you post an excerpt of your debug output so that I know which function / file complains?
My question is what is the proper way to deal with ungraceful disconnections using the sequential API? Am I doing something wrong, should netconn_write return an error for ungraceful disconnections, or is there any other way to check if for connection timeouts?
Unfortunately, there is only RX timeout currently. TX timeout is planned, I think...


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