[lwip-users] trouble sending data between sockets over loopback

[Timm Hannon]

Hi,

I am currently using lwIP in a multi-threaded environment.  
>From the user list it's clear that reading and writing from different 
threads is unsupported, but what about have two threads in a system that
 communicate over the sockets?  I am running on an embedded platform 
that doesn't have an ethernet if, it just sends and data internally 
between sockets over the network stack on the loopback if.  Should this 
work?

My thread setup is as follows:
Thread 1: This thread waits on 
select for one side of all open connections.  It reads data from a 
socket if it is ready and sends any data that it needs to its sockets.  
This is the main thread that creates connections when needed.
Thread 2: This is a thread that waits on a listen on a port for 
connections from thread 1.  If it receives a connection it spins off a 
new thread with the socket that was created.
Threads 2.1-2.x: Is 
passed the socket created from thread 2 and sends and receives data 
between itself and thread 1.  There is one of these threads for every 
connection made between
Thread 3:  Same as thread 2, just a different port.
Threads 3.1-3.x: 
Same as threads 2.1-2.x.

If I only create one connection between 
thread 1 and 2 (spinning off only thread 2.1), everything works 
correctly.  If, however, I make simultaneous connections to thread 2 and
 3 or multiple connections to thread 2 (spinning off more than 1 thread 
waiting on the same port but different socket) the system is left with 
unacked data in the queue.

Doing some basic debugging it looks like the data is still in the 
system, but doing a read select on the port that should be receiving the
 data, doesn't return that their is data ready. 

I can also 
provide my settings files and debug output if needed/helpful.

Thanks for your help,
Timm