I wrote a small TCP servers with
The usual pattern is to use non-blocking file descriptors with
poll() like this:
POLLINbecause you are always interested in reading what the other end of the socket has send you.
POLLOUTonly if you have outstanding data to send to the other end.
poll(), if it indicates that data is available to read,
poll(), if it indicates that the socket is writable,
POLLOUTnext time through the loop
POLLOUTthe next time through the loop.
POLLOUTthe next time through the loop only if there was some data left.
POLLOUTthe next time through the loop. (This choice is often easier to program because you only need to handle writing data in one place in your loop but on the other hand it delays writing the data until the next time through the loop.)