[lwip-users] File transfer over TCP/IP

[Peter Jančo]

Hi,
I write FTP server on LPC2478 and uEZ1.11 platform.
There is a simple loop where is recieving data from FTP client.



struct netbuf *inbuf;

while(1)
{     
        inbuf = NULL;
        inbuf = netconn_recv(conn_data);
        if(inbuf)
        {
            netbuf_copy(inbuf,BlockBuffer,inbuf->ptr->tot_len);
            UEZFileWrite(file,BlockBuffer,inbuf->ptr->tot_len,NULL);//store data to filesystem
            netbuf_delete(inbuf);
        }
        else
            break;
}



FTP client (Total Commander) split the big file into few packets. For example file with total length 9130B is split like this:
512B,988B,1460B,1460B,1460B,1460B,1460B,40B,290B

First 8 packets is received always fine. The last packet (290B) is received just sometimes. So the received file have length only 8840B. Connection timeout is set to 0 (infinite).

I have captured ethernet communication between FTP server (LPC2478) and FTP client (my PC). LPC2478 don't recieve 290B packet at first attempt. After that PC send retransmission with data length 330B. I don't understand why. This is not the same packet which I lost. Data in this packet is identical like in the 40B packet and 290B together. After them is connection closed.

Why I have problem with receiving the last data packet?

Best regards Peter Janco.