Re: [lwip-users] Telnet - Raw API

[Sergio R. Caprile]

A pbuf can be a single one or a chain of them, and your app gets what 
the rx driver got, so most likely you can't tell in advance and have to 
be prepared to just deal with it.
If you can spare the memory, you can copy to a buffer and be happy. But 
if you can't spare it, there are pbuf_ functions that provide some basic 
operations for typical actions on typical application work; like 
searching for a string.
In a web server, for example, you need to parse the host headers, but 
they can come in several frames (due to TCP operation), and those frames 
may themselves be chains of pbufs (due to memory fragmentation). A 
common practice is to intentionally chain incoming pbufs until you get 
the expected length, and then parse the pbuf chain for the expected 
data. If memory is available, you might just copy everything to a big 
enough buffer.