Re: [lwip-users] Releasing pcb after tcp_new()

[address@hidden]

Bill,

isn't the sent callback enough to keep track of data that is sent 
successfully? Other than that, data should be deallocated when calling 
tcp_close(), which results in deleting the pcb sooner or later...

Rick,

the solution to deallocate the pcb is simply calling tcp_close() for 
that pcb. Based on the state of the pcb, it will be deallocated 
instantly or go through some wait states. But it will eventually get 
deallocated. When bind fails, the pcb should be in CLOSED state and 
should be deallocated right away. But what you say sounds kind of wrong 
- that you couldn't create a second listening connection after closing 
the first... I'll try to check that in the code.

Simon


Bill Auerbach schrieb:
> Rick,
>
> We’re going down the same path, more or less. One thing to watch on 
> tcp_close is the tcb_pcb isn’t actually finished being used until 
> later – one of the tcp timers is completing the connection. This ties 
> up pcbs internally for older connections until they are closed. 
> Allocate MEMP_NUM_TCP_PCB to twice what you think – or more if you are 
> opening and closing connections a lot.
>
> One thing I would like to see is a callback when the pcb is going to 
> be deallocated so that dynamic memory associated with it can be 
> released when the data is sent and the connection completes later. 
> Maybe someone knows already how to do this?
>
> Thanks,
>
> Bill Auerbach
>
> ------------------------------------------------------------------------
>
> *From:* address@hidden 
> [mailto:address@hidden *On 
> Behalf Of *Rick Culver
> *Sent:* Wednesday, January 09, 2008 12:29 PM
> *To:* address@hidden
> *Subject:* [lwip-users] Releasing pcb after tcp_new()
>
> I am using CALLBACK API and set up a pcb using tcp_new() followed by 
> tcp_bind() followed by tcp_listen() & tcp_accept(). In my accept() for 
> a valid connection I use tcp_close() to close the LISTEN connection to 
> avoid any additional connection requests for a new connection. When I 
> am done using the connection I use tcp_close() to shut it down and 
> then repeat the process with tcp_new() to start a new LISTEN port. My 
> problem is 2 fold.
>
> First I find that the 2nd time through the tcp_bind() function I get 
> an ERR_USE return which appears to be caused by the active list of pcb 
> still having the old port number in it. I think ther is a problem with 
> tcp_bind() which causes this to happen.
>
> Secondly (and the biggest problem) is that once I get the ERR_USE then 
> I have a pcb allocated and this consumes pcb space and I eventually 
> run out of space. So the question is, if I get an error with 
> tcp_bind() how can I release the pcb allocated by the tcp_new() so I 
> do not consume pcb memory space and fill it up. I think there could be 
> a problem with tcp_bind() giving this error which is also an issue. 
> Can anyone suggest how to approach these problems?
>
> Rick
>
> ------------------------------------------------------------------------
>
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