Re: [lwip-users] Sharing TCP port

[Danish Ali]

Thanks for your response, Simon. But I fear we are talking at 
cross-purposes.

I already have working code with LWIP being the server on 5060, and 
accepting multiple simultaneous TCP links that remote devices call into 
LWIP.

So I think I have already done your suggestion of

> 1 listener -> accept -> multiple connection sockets?


But now I want to be able, at the same time, to have LWIP make 
connections _from_ its TCP port 5060 _to_ other, different and currently 
unconnected, remote devices.

So the local port is always 5060. And I have one netconn listening for 
incoming TCP connection attempts from any IP-address. And each fresh 
incoming TCP gets assigned to a fresh netconn. And this works.

Now how do I set up a netconn to be coming from 5060 and going to a 
specified new IP-address:port (for which I don't have an open link)?

I might add that I come from a "bare metal" microcontroller background 
rather than a Unix sockets background. I don't know how one would write 
it for sockets. I have tried to look (for example) at the pjsip 
source-code and that does not seem to assign the port number for its 
outgoing TCP connections.

Is this something that should be possible? Do you have a link that might 
give me a clue (even if it is written for sockets rather than netconn?)

Regards,
Danish

> Message: 2
> Date: Mon, 15 Mar 2021 16:23:34 +0100
> From: "goldsimon@gmx.de" <goldsimon@gmx.de>
> To: Mailing list for lwIP users <lwip-users@nongnu.org>
> Subject: Re: [lwip-users] Sharing TCP port
> Message-ID: <b5a5a3bc-07a1-5ca0-dce2-6b2a09da13d3@gmx.de>
> Content-Type: text/plain; charset=utf-8
>
> Am 15.03.2021 um 16:15 schrieb Danish Ali:
> > I would like to be able to have multiple simultaneous TCP links to a
> > single port (in my case 5060 for SIP).
>
> Try to write the same thing for standard sockets. If you know that API,
> transforming the code to use the netconn API pretty simple.
>
> And for sockets, there are *much* more exampes and places to ask.
>
> I assume what you're missing is: 1 listener -> accept -> multiple
> connection sockets?
>
> Regards,
> Simon