Re: [lwip-users] TCP_SNDBUF limit

[Gaurav Jain]

Thanks for the response. Actually I framed the question a bit wrong.
So I have this situation, where my windows client sends 9KB data to
lwip server (on Virtex 7). Now once the server has received the data,
it processes it and sends it back. However, the transmission fails
beyond 8KB because the tcp_sndbuf is not reset and its limit reached.
So on analyzing the packets through wireshark, I observed that the
after the client completes it sending, its ack no. is 9217, i.e. it is
expecting a packet with seq no 9217. However, on the server side,
since I have initiated the sending, it sends the packets from seq 1.
Due to this, the server keeps on sending the data to the client, which
receives the data, but does not send back an Ack. How I know it
receives the data because the data is being written into file.

Some help about where I am going wrong would be grateful.

On Fri, Feb 5, 2016 at 4:54 AM, Joel Cunningham <address@hidden> wrote:
> The LwIP master branch supports larger windows than 65535 by enabling the
> window scaling options.  So no patches should be needed.  Check out
> LWIP_WNDW_SCALE and TCP_RCV_SCALE in opt.h
>
> Joel
>
> On Feb 04, 2016, at 03:36 PM, Michael Steinecke <address@hidden>
> wrote:
>
> That depends on your config file. Natively you can send up to 65535 bytes in
> one TCP transmission. As far as I remember, its the TCP_WND #define,
> controlling this. If you need more bigger massages, you need to replace a
> lot of u16 by u32. There is also an oversize patch somewhere, doing this
> correctly.
>
> 2016-02-04 8:00 GMT+01:00 Gaurav Jain <address@hidden>:
>>
>> Is there a limit on the tcp send buffer? What I have observed is, that
>> If I try to send huge amount of data in chunks, it accumulates it upto
>> 8192 (8K) and then gives out No Space in Send buffer.
>>
>> Do we have to reset the buffer or we can call tcp_output(pcb) so that
>> the data fargments are sent immediately?
>>
>> Gaurav
>>
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