Re: [lwip-users] Raw api + multiple TCP Connections

[Noam Weissman]

Hi,

 

First of all read the lwip readme and every document you can find.

 

Check the echo server example and see how it is written.

 

1.

If both servers are the same write functions and simply pass parameters. You do not need

to copy and paste the same code. Use the arg parameter in the call backs

 

2.

If you use Lwip 1.41 the tcp_accepted function should accept the SERVER pcb and not the new connection pcb

 

When you write a TCP server and bind it to port_x it means that the server is listening on that port.

Listening means it can accept several connections at the same port.

 

The data transfer is not handled via the listening port but rather working port. Every connection gets a working

different port… that’s TCP !!!.

 

Your accept function is wrong. Here is my fast created code based on yours. Check it and see if it helps

 

If you do not need two servers but rather two connections there is no need to create two servers !!!

 

// Define type

typdef struct

{

  struct tcp_pcb *ServerPcb;

  u16 ServerPort;

 

} MyServer_t;

 

//---------------------------------

 

// define server variables at the same file you call init_Server function

static MyServer_t Server_1, Server_2;

 

// initialize server settings

Server_1.ServerPcb = NULL;

Server_1.ServerPort = PortCAN1;

 

Server_2.ServerPcb = NULL;

Server_1.ServerPort = PortCAN2;

 

//----------------------------------------------

 

// function protoypes

static err_t myAccept(void *arg, struct tcp_pcb *pcb, err_t err);

static err_t myRecvCallback(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err);

 

 

// code start in main or what ever...

 

init_Server(&Server_1);

init_Server(&Server_2);

 

 

//---------------------------------------------------------------------------

//---------------------------------------------------------------------------

 

// initialize servers

void init_Server(MyServer_t *Server)

{

  struct tcp_pcb *pcb;

  err_t err;

 

 

  // create new pcb 

  pcb = tcp_new();

 

  if(pcb != NULL)

  {

    // bind port

    err = tcp_bind(pcb, IP_ADDR_ANY, Server->ServerPort);

 

    if(err == ERR_OK)

    {   

      // save server pcb for later use, not the same !

      Server->ServerPcb = tcp_listen(pcb);

   

      // if needed ???

      tcp_setprio(Listening_pcb, TCP_PRIO_MIN); 

  

      // save argument for later use

      tcp_arg(Server->ServerPcb, Server);

 

      // define accept call back

      tcp_accept(Server->ServerPcb, accept);

    }

    else

    {

      // add error handling

    }

  }

  else

  {

    // add error handling

  }

}

 

//---------------------------------------------------------------------------

 

static err_t myAccept(void *arg, struct tcp_pcb *pcb, err_t err)

{

  MyServer_t *Server = (MyServer_t*) arg;

 

 

   // if needed ????

   // disable nagle algorithm, improve performance with winxp.

   tcp_nagle_disable(pcb);

 

 

  // do you really need TCP_PRIO_MAX ???

  tcp_setprio(pcb, TCP_PRIO_MAX);

 

  // assign recv callback, only one function needed

  tcp_recv(pcb, myRecvCallback);

       

 

  // if you use Lwip 1.41

  tcp_accepted(Server->ServerPcb);

      

  return ERR_OK;

}

 

//---------------------------------------------------------------------------

 

static err_t myRecvCallback(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err)

{

  char data[8] = {1,2,3,4,5,6,7,8};

 

  // avoid compiler warnings

  ( void ) arg;

  ( void ) err;

 

  if (!p) //end of linked list

  {

    tcp_close(tpcb);

    tcp_recv(tpcb, NULL);

    return ERR_OK;

  }

 

  tcp_recved(tpcb, p->tot_len); //Antwort

 

  tcp_write(tpcb, &data[0], 8, TCP_WRITE_FLAG_COPY);

  tcp_output(tpcb);

  pbuf_free(p);

 

  return ERR_OK;

}

 

 

I hope I do not have errors… wrote it fast J.

 

 

BR,

Noam.

 

 

 

 

From: lwip-users [mailto:lwip-users-bounces+address@hidden On Behalf Of Werner Motz
Sent: Monday, May 22, 2017 2:38 PM
To: 'Mailing list for lwIP users'
Subject: Re: [lwip-users] Raw api + multiple TCP Connections

 

U are right, but I don’t know where the mistake is. I can debug it and the breakpoints in myCallback1 and myCallback2 are hit.

The also debugged the init_Server and the binding or listen gave no error. Both connections are initiated correctly.

 

 

I do init:

 

void init_Server(void)

{

struct tcp_pcb *pcb_1;

struct tcp_pcb *pcb_2;

 

pcb_1 = tcp_new();

pcb_2 = tcp_new();

 

tcp_bind(pcb_1, IP_ADDR_ANY, PortCAN1);

tcp_bind(pcb_2, IP_ADDR_ANY, PortCAN2);

 

       pcb_1->flags |= TF_NODELAY;

       pcb_1->flags |= TF_ACK_NOW;

 

pcb_2->flags |= TF_NODELAY;

       pcb_2->flags |= TF_ACK_NOW;

 

       tcp_arg(pcb_1, pcb_1);

tcp_arg(pcb_2, pcb_2);

 

       pcb_1 = tcp_listen(pcb_1);

pcb_2 = tcp_listen(pcb_2);

 

       tcp_accept(pcb_1, accept);

tcp_accept(pcb_2, accept);

}

 

 

static err_t accept(void *arg, struct tcp_pcb *pcb, err_t err)

{

       LWIP_UNUSED_ARG(arg);

       LWIP_UNUSED_ARG(err);

 

       // set the receive callback for this connection

       if(pcb->local_port == PortCAN1)

       {

             tcp_setprio(pcb, TCP_PRIO_MAX);

             tcp_recv(pcb, myCallback1);

       }

       else if(pcb->local_port == PortCAN2)

       {

             tcp_setprio(pcb, TCP_PRIO_MAX);

             tcp_recv(pcb, myCallback2);

       }

      

       // just use an integer number indicating the connection id as the

       // callback argument

       tcp_arg(pcb, (void*)pcb);

 

 

       // Inform lwIP that an incoming connection has been accepted.

       tcp_accepted( pcb );

      

       return ERR_OK;

}

 

 

static err_t myCallback1(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err)

{

       // avoid compiler warnings

       ( void ) arg;

       ( void ) err;

       char data[8] = {1,2,3,4,5,6,7,8};

 

       if (!p) //end of linked list

       {

             tcp_close(tpcb);

             tcp_recv(tpcb, NULL);

             return ERR_OK;

       }

 

       tcp_recved(tpcb, p->tot_len); //Antwort

      

       tcp_write(tpcb, &data[0], 8, TCP_WRITE_FLAG_COPY);

       tcp_output(tpcb);

       pbuf_free(p);

      

       return ERR_OK;

}

 

 

static err_t myCallback2(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err)

{

       // avoid compiler warnings

       ( void ) arg;

       ( void ) err;

       char data[8] = {1,2,3,4,5,6,7,8};

 

       if (!p) //end of linked list

       {

             tcp_close(tpcb);

             tcp_recv(tpcb, NULL);

             return ERR_OK;

       }

 

       tcp_recved(tpcb, p->tot_len); //Antwort

      

       tcp_write(tpcb, &data[0], 8, TCP_WRITE_FLAG_COPY);

       tcp_output(tpcb);

       pbuf_free(p);

      

       return ERR_OK;

}