Detecting unexpectedly closed sockets

Alex Tweedly alex at
Sun Oct 17 07:11:22 EDT 2004

At 11:32 17/10/2004 +0200, Tomas Franzén wrote:

>>Finally, always keep your keep alive packets to a size small enough to 
>>fit into one single ethernet packet. Don't exceed that length for 
>>something as simple as a keep alive.
>As you can see, my requests are not very small. A keep-alive might look 
>like this, I suppose:
>Request-Id: 123
>Will this fit into a single ethernet packet? I don't know much about this 
>kind of lower level stuff.

Yes, that should be OK. You can reasonably assume that an ethernet packet 
can hold at least 576 bytes. You use up 20 for UDP/IP headers, or 40 for 
TCP/IP, and you can use up a few more on obscure lower level stuff. It's 
pretty safe to assume 500 bytes of application payload.

>>Ah, network protocol design, fun stuff.
>Indeed. :-)
>In my situation, I use two kinds of clients, the 'master' (teacher), and 
>the 'client' (student), and both connect to the main server, which keeps 
>track of who is online. Also, the student is a server, too, responding to 
>commands from the master. Ah, tricky stuff.

And presumably the student can ask a question - which means (in network 
terms) the teacher client must respond to something initiated by the 
student. So you get all the complexities of peer-peer.

Have fun ...
-- Alex.

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