Hello, 
I am using LWIP stack (2.0.2) with pppos.I have NXP MC5748 board with SIM800c 
interface with one UART channel.I have used AT commands to configure GSM 
module. 
I am trying to send data to server using LWIP socket programming.
Steps of programming:
1. lwip_socket(PF_INET, SOCK_STREAM, 0);
2. lwip_connect(socket_fd,(struct sockaddr_in*)&sa,sizeof(struct sockaddr_in));
3. lwip_write(socket_fd, "test", 4);
After step 3. i am able to send "test" to server, But in next step i am sending 
again data to server 
And code get stuck in "LWIP_ASSERT("unsent_oversize mismatch (pcb vs. 
last_unsent)",pcb->unsent_oversize == last_unsent->oversize_left);"
My oberservation while debugging is , After connect call only once system 
sending data to server and while sending second time it getting stuck as i 
mentioned above. 
during this  condition,  last_unsent->oversize_left = 0. 
And pcb->unsent_oversize = 124 (When  TCP_MSS = 128 and TCP_SND_BUF =256) ,my 
data length was 4.
I have also tried other values for TCP_MSS  and TCP_SND_BUF like  1024 and 2048 
 respectivly

So please help to sort out this issue, Why code is getting stuck while sending 
data second time. And To solve this issue, Do i need to do any specific setting 
in  PPPOS configuration?  Thanks, Rahul
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