[Click] How to establish a TCP connection and generate TCP flows

[Harald Schioeberg]

On Tue, 2010-11-23 at 21:36 +0100, Manel.Bourguiba at lip6.fr wrote: 
> Thanks for your answers.
> I had a look at the thesis that proposed TCPSpeaker. It seems  
> interesting to use this element. But the only example given is in the  
> case of a proxy. My need is much simpler: two hosts: one source and  
> one sink communicating with TCP.
> So how to generate the flow in the source and send it to the sink?  
> let's say with RatedSource, can I have (in the source) roughly  
> something like :
> RatedSource (...) -> [0]TCPSpeaker
> TCPSpeaker[0] -> ToDevice(eth0)
> FromDevice (eth0) -> [1]TCPSpeaker
> TCPSpeaker[1] -> ToDevice(eth0)
> 
> Actually, I didn't understand the utility of having two output and two  
> inmput ports.

because TCP establishes bi-directional connections, while click ports
are uni-directional so you need pairs. You cannot separate the
directions into 2 Elements, since ACKs and data is transported on the
same packet for the different directions.
If you only need unidirectional transport, connect the remaining ports
to Idle/Discard.

Your example is exactly right, just make sure that TCPSpeaker gets valid
TCP/IP or UDP/IP encapsulated packets. 

No need to worry about seq &co, just the IP Address and Port fields must
be filled correctly, so that TCPSpeaker can associate it with a
connection. TCPSpeaker accepts either TCP or UDP Packets, but will
always emit TCP packets. 

There is some doxygen in the sources, but I'm not too proud of it :(

Dan wrote a Master Thesis using and profiling the code, here it is: 
http://www.net.t-labs.tu-berlin.de/papers/L-TCMWMN-10.pdf
It's probably the best documentation that is available. 

Hope that helps. 
Harald