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

[Bill Auerbach]

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

 

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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