[lwip-users] Re: lwip connect to normal socket application very very slowly

[cyhong]

>> From: address@hidden
>> To: address@hidden
>> Subject: lwip connect to normal socket application very very slowly
>> X-Mailer: Lotus Notes Release 5.0.11   July 24, 2002
>> Date: Mon, 4 Sep 2006 10:40:32 +0800
>> 
>> If I use LWIP to send packets to a linux  server (a normal socket 
>> application), 
>> the linux socket application will reply ACK very very slowly......
>> 
>> but if I use a linux client( a normal socket application)  to send packets 
>> to a linux  server (a normal socket application)
>> the linux socket application will reply ACK very very fast......

>How slow is "very very slowly".  Can you provide a packet trace
>(e.g. from ethereal or tcpdump) to illustrate your problem?

>Kieran


I have found out the problem.....
linux socket program will use NAGLE/delayed ACK...algorithm.

If I use "tcp_write();tcp_output();" to send a packet(1024 bytes ) to the linux socket prgram!!
it will reply me a ACK after 0.1~0.2 sec, it is too long!!
Even if I set URG,PSH tcp flags inside the packet, it is the same !!

linux socket program will insist on replying me ACK after after 0.1~0.2 sec!
and inner LWIP seems to insist on receiving ACK (belong to previous packet) and then send next packet!!


Why I said it is very very slowly.....
If I use two linux socket program to communicate with each other!!!
They will send two packets (1024 bytes), and wait only one ACK, just after 0.0001~0.0002 sec.


Could anybody know how can I push the other side (linux socket program) reply me more quickly?


ps. I have a bad solution, I send packets doubly (when using LWIP), and linux socket program will reply quickly!!

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