[lwip-users] LWIP server fails if we connect multiple clients

[Kranti P]

Hi All,

 

I am facing problem when I connect multiple clients to lwip server.

It works fine for single client.

When I connect multiple clients, after some time I get, tcp_write out of memory error.

Clients having interframe delay 10ms.

 

Please suggest me a solution.

 

My opt.h settings are as below,

 

#define NO_SYS                                    1

#define TCP_TMR_INTERVAL          250
#define TCP_SND_BUF                  5840
#TCP_MSS                                 1460
#define MEM_SIZE                       64000
#define MEMP_NUM_TCP_PCB                             16
#define MEMP_NUM_TCP_PCB_LISTEN       50
#define MEMP_NUM_TCP_SEG                            50
#define TCP_WND                                            (4 * TCP_MSS)
#define TCP_SND_QUEUELEN                             ((4 * (TCP_SND_BUF) + (TCP_MSS - 1))/(TCP_MSS))

 

Server code:

signed int prvxMBTCPPortReceive(void *arg, struct tcp_pcb *pxPCB, struct pbuf *p, signed int Err)

{

 

            unsigned char *pModbusHeader;

            u16_t len;

            signed int Error;

            tcp_nagle_disable(pxPCB);

            if( Err != ERR_OK )

            {

                        return Err;

             }

    if( p == NULL )                                                                                          // If pbuf is NULL then remote end has closed connection.

            {

                        prvvMBPortReleaseClient( pxPCB );

                        return ERR_OK;

             }

 

            len = p->tot_len;

            pModbusHeader = p->payload;

 

 

            MODTCP1 = ((struct mod_tcp_hdr1 *)pModbusHeader);

            Trans_id = MODTCP1->trans_id;

            Proto_ID = MODTCP1->proto_id;

            Len = MODTCP1->len;

            tcp_recved(pxPCB, p->len);

            tcp_tmr();

 

            memcpy( Comm3Buff, pModbusHeader + 6, (unsigned short) *(pModbusHeader + 5) );

            ReceiveBuffLength3 = len - 6;

            ProcessSerialIntr3();

            //pcb->snd_queuelen =0x00;

           

                       

            MODTCP1 = ((struct mod_tcp_hdr1 *)&RxBuff[usTCPBufPos]);

            MODTCP1->trans_id = Trans_id;

            MODTCP1->proto_id = 0;

            MODTCP1->len =  htons((unsigned short)(FrameLength3-1));

 

            memcpy( &RxBuff[usTCPBufPos + 6], Comm3Buff, (unsigned short) (FrameLength3 - 1) );

            if( (Error = tcp_write( pxPCB, RxBuff, (unsigned short) (6+FrameLength3-1), 01 )) == ERR_OK )

{

                                    ( void )tcp_output( pxPCB );                                                                                            //Make sure data gets sent immediately

                        }

                        else

                        {

                                               

                                    prvvMBPortReleaseClient( pxPCB );                                                                                // Drop the connection in case of an write error.

                        }

                        usTCPBufPos = 0;                                                                                                                                        // Reset the buffer.

                       

                        pbuf_free( p );

                        return ERR_OK;

}

 

Waiting for your reply,

 

 

 

Thanks & Regards,

Kranti Patil,

Embedded  Engineer,

REPL | PUNE | INDIA.