Re: [lwip-users] tcp_write problem after the first transmission

[Daniel Berenguer]

That makes a lot of sense.

Thanks guys for your help. I'll try out what you suggest.

Daniel.


2010/1/27 address@hidden <address@hidden>:
> As a side note, I hope you are calling the loop below in the tcpip_thread,
> not from another application thread, which would violate lwIP threading.
>
> Aside from that, what Bernhard said is true: the packets are buffer for
> retransmission until they are ACKed by the remote side, which cannot happen
> while you are in the loop. As a result, you either have to bufer your data
> somewhere else and call tcp_write() from the 'poll' or 'sent' callback - or
> increase TCP_SND_QUEUELEN to 20 (in your case, depends on your application)
> to be able to internally queue as much data as you have to at maximum.
>
> Simon
>
>
> Daniel Berenguer wrote:
>>
>> I'm trying to send a bunch of TCP packets using the raw API but
>> tcp_write is returning -1 (out of memory) after the 8th packet.
>>
>> for (i=0 ; i<20 ; i++)
>> {
>>     strcpy(buffer, "holaaa");
>>     res = tcp_write(pcb, buffer, 7, 0);
>>     tcp_output(pcb);
>> }
>>
>> I've used many variants of the above code (with delays, w/o
>> tcp_output, ...) but the problem is always there. The first packet is
>> sent immediately after the first tcp_write but then, tcp_write just
>> pushes the packets into the sending queue. TCP_SND_QUEUELEN is set to
>> 8 so once the TX queue gets overflowed tcp_write starts returning -1
>> and the contents of the queue is finally sent (only 7 packets of 20
>> though).
>>
>> Any idea?
>>
>> Thanks.
>>
>>
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>>
>>
>
>
>
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