Re: [lwip-users] TCP Disconnect Detection lwIP V1.2

[address@hidden]

Questions like this one are often asked here. In fact, TCP is not really 
helpful here. There are a few parameters to tweak to make TCP detect 
connection errors earlier, but most of them have some side-effects so 
that you really have to know what you are doing.

What you are doing is already the best solution, I guess: design the 
communication protocol in a way that always at least a little data is 
being sent so that the other end can detect when that data doesn't come.

Regarding the connection closure, that depends on the protocol being 
used: raw API returns a null pbuf, the other APIs have other means to 
tell you the remote side closed - but all this happens only after large 
timeouts when using the default TCP parameters.

Simon


Gurpal Gill wrote:
> Hello,
>  
> I'm wondering how to detect that a TCP connection has been closed? 
> Also, if a connection were to get disconnected via a power outage 
> (simulated by disconnecting the ethernet cable from the device)? 
> Currently I transmit a byte of data every 15secs of no activity and 
> when I get an error I close the connection. I need a better way since 
> the application on the other end has to process the byte that I'm 
> sending which causes problems. I'm using lwIP with the xilinx tools 
> (S3ADSP1800A eval board). Just a note, I'm using lwIP in non blocking 
> mode so the read command either returns -1 or the number of bytes 
> read. Any help would be appreciated.
>  
> Regards,
>  
> Gurpal Gill
> ------------------------------------------------------------------------
>
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