Re: [lwip-users] Choosing the right lwip API...

[Jonathan Larmour]

DownyTif wrote:
> Hi all,
>
> I was wondering what API I should use to do what I want to do. By the way,
> I'm new to the mail-list/forum and lwip world. I tried to find the
> differences between the Raw, sockets or sequential (netconn) APIs, but I
> haven't found anything useful.

http://lwip.wikia.com/wiki/LwIP_Wiki has a lot of stuff about the APIs. In 
essence the raw API is event-driven, the sequential (netconn) API, is a 
more traditional API with calls to e.g. netconn_write() which can block 
until the operation completes, and the sockets API is the same sort of 
thing as the sequential API, but using the well-known BSD sockets 
functions (like socket(), bind(), listen() accept(), etc.).

Each API (raw->sequential->sockets) in turn has more overhead (both code 
and data) and is slightly slower than the previous one, and for some 
hardware, you can get much better performance with the raw or sequential 
APIs than the sockets API in some situations, but that doesn't mean the 
sequential or sockets APIs are slow. If performance is critical for you 
(and your other mail implies this might be tree) it could be that the raw 
API is a better choice. Although you have to do more things yourself with 
the raw API.

> So, I was thinking that maybe the sequential API (netconn) was not the way
> to go.

It's unrelated to your other mail about large packet sizes. An 
event-driven model such as the raw API affects your program design a lot. 
Some people like the familiarity of the sockets API if they've used it 
elsewhere, or if they are reusing existing code. It's a choice with 
trade-offs between them, which is why lwIP has all three!

Jifl
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