CODEWITHSUNDEEP
cembeddedrtoslwip
Necrotos
Necrotos

Reputation: 81

LwIP Clilent can't establish a connection

I want to connect two F746ZG boards so that they can communicate via TCP. I am using the STM implementation of LwIP with the netconn API. The IP address is supplied via DHCP, but it is always the same address. Also, the address matches the expected value. The problem I am facing is that the client seemingly can't establish a connection. I am binding the connection to port 8880. Since I ran into this issue, I have written a debug client that should just periodically send a predefined message to a server. Here is the code for the client:

static void tcpecho_client_thread(void const *arg)
{
  struct netconn *xNetConn = NULL;

  err_t bind_err, connect_err;

  char* b_data = "OK"; // Data to be sent
  uint16_t b_len = sizeof ( b_data );

  IP4_ADDR(&local_ip, IP_ADDR0_CLIENT, IP_ADDR1_CLIENT, IP_ADDR2_CLIENT, IP_ADDR3_CLIENT);
  IP4_ADDR(&pc_ip, IP_ADDR0_PC, IP_ADDR0_PC, IP_ADDR2_PC, IP_ADDR3_PC);

  xNetConn = netconn_new ( NETCONN_TCP );
  if (xNetConn != NULL){
      bind_err = netconn_bind ( xNetConn, &local_ip, TCP_PORT_NETCONN );

      if(bind_err == ERR_OK){

          // Try to connect to server
          for(;;){
              connect_err = netconn_connect ( xNetConn, &pc_ip, TCP_PORT_NETCONN);

              if (connect_err == ERR_OK){
                  // We are connected
                  while(1){
                      BSP_LED_On(LED1);
                      netconn_write(xNetConn, b_data, b_len, NETCONN_COPY);
                      vTaskDelay(1000); // To see the result easily in Comm Operator
                  }
              }
          }
      }else{
          // Failed to bind the connection
          BSP_LED_On(LED3);
      }
  }else{
      // Failed to allocate a new connection
      BSP_LED_On(LED3);
  }

}

When I debug this, netconn_connect never manages to actually connect to something. Since I am able to ping the board and get a response, I am confused, what is going wrong here. I have tried to use Hercules to set up a TCP server on my PC so that the board can connect to that, but that also doesn't work. Using Wireshark, I can see the responses to my ping command coming in, but I don't see anything that would indicate the board trying to connect to my PC. I have tested the corresponding server on the second board, but that runs fine. I can connect to it with Hercules and send data, so I doubt there is anything fundamentally wrong with the LwIP stack.

What I could guess is that I messed up the netconn_bind, I am not 100% sure what IP you are supposed to bind the connection to. The way it currently is, is how I read the documentation. For the server, I have bound it to IP_ADDR_ANY. Besides that, my implementation mostly matches with the examples you can find online (e.g. LwIP Wiki).

Upvotes: 0

Views: 681

Answers (1)

Necrotos
Necrotos

Reputation: 81

I have figured out the problem. After I delete the netconn_bind call, everything works fine for me.

Upvotes: 0

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