[lwip-users] Raw api + multiple TCP Connections

[Werner Motz]

Hello,

I am using lwip 2.0.2 RAW API and I have a question depending multiple TCP Connections.

I create two connections without problems. Over each of them I can send and receive data.

When a single client sends me data every 1ms, my receive callback function (tcp_recv(pcb, myCallback1)) gets periodically called.

In myCallback1 I handle the received data and answer. This works fine and on Wireshark I am able to reach a

communication rate of about 6Mbit/s without data loss. (lwip stats without errors or drops…)

 

Now if I try to receive data at the same time from the second client (every 5ms) and using annother callback function

(tcp_recv(pcb, myCallback2)) my system crushes (Hard fault Handler).

 

My first thought was that a receive callback cannot be called from two clients at the same time so I did the following:

I synchronized the client’s sending intervals (LabView) and changed the send timing to

Client_1 send ---> 3 ms delay ---> Client_2 send ---> 3ms delay ---> Client_1 send…..

Unfortunately this does not work either although I am sending slower with less data.

 

Now my question: How to handle received data from multiple connections?

1.)    Is there a better way than using two different callback functions? Polling?

2.)    What does lwip do if two clients send me data at the same time?

3.)    Is the receive callback (myCallback1/2) blocking?

 

I debugged my lwip_stats but they show no errors.

I am looking forward to your answer(s).