I am trying to use the lwip stack in freertos for a UDP based communication over multiple sockets. My first problem was, that socket creation failed because, lwip_socket has a call to netconn_new, which contains a call to TCPIP_APIMSG(&msg), which returned with an error. I figured out that the error in TCPIP_APIMSG(&msg) was produced because sys_mbox_valid(&mbox) returned false.
I could solve the problem after recognizing that I created more UDP sockets than allowed by the lwip configuration variable memp_n_udp_pcb. I just increased memp_n_udp_pcb.
Now I have the problem that lwip_sendto stops working after sending about 300 packets. Again, an invalid mbox in TCPIP_APIMSG(&msg) seems to be the reason. lwip_sendto calls netconn_send, which calls TCPIP_APIMSG(&msg), which returns an error due to an invalid mbox.
I am only trying to use the lwip stack with freertos, but I have no experience with the implementation details of the lwip stack. I have no idea what the invalid mbox means and how to solve the problem.
I hope someone can explain to me what is going wrong here.
Are there any further settings (except memp_n_udp_pcb) I have to change when using more than the predefined number of 4 UDP sockets?
Why does lwip_sendto fail after sending a few hundred packets without problems?
