Adriaan Van Steendam

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11 years, 6 months ago.

Net::poll();

This comes from an HelloWorld Server example with the old Ethernet Interface

What does this actually do? Is this like: 

poll() is used to check on the state of a socket in a set of sockets. 
The set can be tested to see if any socket can be written to, 
read from or if an error occurred.

Or does this means:

check WHAT and not IF there is something comming in in the socket.

thnx!

1 Answer

Rod Coleman
11 years, 6 months ago.

With the old LwIP libraries, which cannot run under RTOS, data is not moved anywhere until the net::poll() function is called.

For example, say you have set up a connexion to a remote device (you issued a LwIP tcp_connect() ). This will send the introductory SYN to the remote end, but when you receive some data back, this will not be available until you have called a net::poll().

when the net::poll() is called, the LwIP layer will check the receive buffer for data, and start your receive callback if there is something waiting.

Yes, it's a bit manual-operated - but it actually works very reliably. Used with the LwIP raw TCP or UDP API, it is much more robust than any of the available high-level libraries, IME.

http://lwip.wikia.com/wiki/Raw/TCP

Accepted Answer

thnx for your comment, i posted some new questions about whats going on in the server example. i you have some extra time could you take a look at it? thnx in advance

posted by Adriaan Van Steendam 13 May 2013