[lwip-users] Limited packet size on netconn_recv

[Peter Murphy]

Hello,

 

I’m developing a FTP server to run under lwip and freeRTOS. I can send directory info and files over the FTP data port but when I go to receive a file I get a 20 second delay. WireShark shows the first packet is sent milli-seconds after the ‘150 Opening connection’ message is sent but lwip ignores this packet until the client resends the data with a shorter packet length. The first packet sent is 1460 and the following two retransmits are 1460. The third and subsequent packets are 536 in length. Lwip picks up these short packets and returns them to my thread but only after the delay.

 

In lwipopts.h I’ve set the following:

 

#define TCP_MSS                 1460

#define TCP_WND                 (TCP_MSS * 8)

 

My code simplified :

 

 res = netconn_connect(ftpdata, &data_addr, data_port);

 … send msg 150… on FTP command port

ftpdata->recv_timeout = 10;

do{

buff = netconn_recv( ftpdata );

if(ftpdata->err == ERR_TIMEOUT){

Sleep(5);           // no data, wait & try again

            continue;

}

if(ftpdata->err != ERR_OK) goto FTP_SaveExit;

netbuf_data( buff, (void *)&ptr2, &len ); // locate data in pkt

… copy the data…

netbuf_delete( buff );       // recycle packet buf

 

}while(len !=0);

… send msg 226 (transfer complete)… on FTP command port

 

I must be missing something in the set up any ideas?

 

Thanks

Peter